Stock-Based Compensation Plans (Tables)
   | 
12 Months Ended | 
May 31, 2017  | 
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | 
 
 | 
| Weighted-Average Assumptions | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
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				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
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				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Year ended May 31, 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						2016 
				 | 
				
					 
						  
				 | 
				
					 
						2015 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Performance stock options 
				 | 
				
					 
						  
				 | 
				
					 
						Stock options 
				 | 
			 
			
				| 
					 
						Risk-free interest rate 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				1.3 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				1.2 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				1.9 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				2.1 
				 | 
				
					 
						% 
				 | 
			 
			
				| 
					 
						Dividend yield 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				3.6 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				3.6 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				3.6 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				3.7 
				 | 
				
					 
						% 
				 | 
			 
			
				| 
					 
						Volatility factor 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				0.18 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				0.18 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				0.18 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				0.21 
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Expected option life in years 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				6.5 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				6.1 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				6.1 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				6.0 
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Weighted-average grant-date    fair value of stock options granted (per share) 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				5.97 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				5.74 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				5.25 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				5.68 
				 | 
				
					 
						  
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| Stock Option Activity | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Shares 
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
				
					 
						  
				 | 
				
					 
						remaining 
				 | 
				
					 
						  
				 | 
				
					 
						Aggregate 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						 subject 
				 | 
				
					 
						  
				 | 
				
					 
						exercise price 
				 | 
				
					 
						  
				 | 
				
					 
						contractual 
				 | 
				
					 
						  
				 | 
				
					 
						 intrinsic 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						to options 
				 | 
				
					 
						  
				 | 
				
					 
						per share 
				 | 
				
					 
						  
				 | 
				
					 
						term (years) 
				 | 
				
					 
						  
				 | 
				
					 
						value(1) 
				 | 
			 
			
				| 
					 
						Outstanding as of May 31, 2016 
				 | 
				
					 
						  
				 | 
				4.5 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				37.42 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Granted 
				 | 
				
					 
						  
				 | 
				0.7 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				60.82 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Exercised 
				 | 
				
					 
						  
				 | 
				(0.9)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				34.26 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Forfeited 
				 | 
				
					 
						  
				 | 
				(0.1)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				45.95 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Expired 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				36.01 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Outstanding as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				4.2 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				42.02 
				 | 
				
					 
						  
				 | 
				6.3 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				73.4 
				 | 
			 
			
				| 
					 
						Exercisable as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				2.5 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				35.80 
				 | 
				
					 
						  
				 | 
				5.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				58.1 
				 | 
			 
		  
		
			
		 
		
 | 
			 
				 (1)
			 
		 | 
 | 
			 
			Market price of the underlying stock as of May 31, 2017 less the exercise price. 
 | 
 
  
		
			
		 
		  
	   
 | 
| Other Information Pertaining to Stock Option | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Year ended May 31, 
				 | 
			 
			
				| 
					 
						In millions 
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						2016 
				 | 
				
					 
						  
				 | 
				
					 
						2015 
				 | 
			 
			
				| 
					 
						Total intrinsic value of stock options exercised 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				23.8 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				14.5 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				17.6 
				 | 
			 
			
				| 
					 
						Total grant-date fair value of stock options vested 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				4.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				4.0 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				3.6 
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| RSU Activity | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
				
					 
						  
				 | 
				
					 
						remaining 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						grant-date 
				 | 
				
					 
						  
				 | 
				
					 
						vesting 
				 | 
				
					 
						  
				 | 
				
					 
						Aggregate 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						fair value 
				 | 
				
					 
						  
				 | 
				
					 
						period 
				 | 
				
					 
						  
				 | 
				
					 
						 intrinsic 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						RSUs 
				 | 
				
					 
						  
				 | 
				
					 
						per share 
				 | 
				
					 
						  
				 | 
				
					 
						(years) 
				 | 
				
					 
						  
				 | 
				
					 
						value(1) 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2016 
				 | 
				
					 
						  
				 | 
				1.8 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				37.58 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Granted 
				 | 
				
					 
						  
				 | 
				0.6 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				53.76 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Vested 
				 | 
				
					 
						  
				 | 
				(0.6)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				35.43 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Forfeited 
				 | 
				
					 
						  
				 | 
				(0.2)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				42.23 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				1.6 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				43.53 
				 | 
				
					 
						  
				 | 
				2.9 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				97.2 
				 | 
			 
		  
		
			
		 
		
 | 
			 
				 (1)
			 
		 | 
 | 
			 
			Intrinsic value for RSUs is based on the market price of the underlying stock as of May 31, 2017. 
 | 
 
  
		
			
		 
		  
	   
 | 
| Other Information Pertaining to RSUs | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Year ended May 31, 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						2016 
				 | 
				
					 
						  
				 | 
				
					 
						2015 
				 | 
			 
			
				| 
					 
						Weighted-average grant-date fair value per share of RSUs granted 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				53.76 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				42.60 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				36.64 
				 | 
			 
			
				| 
					 
						Total intrinsic value of RSUs vested 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				32.3 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				25.9 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				21.7 
				 | 
			 
			
				| 
					 
						Total grant-date fair value of RSUs vested 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				19.3 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				17.3 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				14.8 
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| Restricted Stock Activity | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						grant-date 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Restricted 
				 | 
				
					 
						  
				 | 
				
					 
						fair value 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						shares 
				 | 
				
					 
						  
				 | 
				
					 
						per share 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2016 
				 | 
				
					 
						  
				 | 
				0.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				43.99 
				 | 
			 
			
				| 
					 
						Granted 
				 | 
				
					 
						  
				 | 
				0.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				60.83 
				 | 
			 
			
				| 
					 
						Vested 
				 | 
				
					 
						  
				 | 
				(0.1)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				42.87 
				 | 
			 
			
				| 
					 
						Forfeited 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				48.61 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				0.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				53.05 
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| Other Information Pertaining to Restricted Stock | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Year ended May 31, 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						2016 
				 | 
				
					 
						  
				 | 
				
					 
						2015 
				 | 
			 
			
				| 
					 
						Weighted-average grant-date fair value per share of restricted stock granted 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				60.83 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				47.46 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				41.70 
				 | 
			 
			
				| 
					 
						Total grant-date fair value of restricted stock vested 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				3.0 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				3.0 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				3.5 
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| Performance Share Activity | 
 
		
			
		 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						grant-date 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Performance 
				 | 
				
					 
						  
				 | 
				
					 
						fair value 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						shares 
				 | 
				
					 
						  
				 | 
				
					 
						per share 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2016 
				 | 
				
					 
						  
				 | 
				0.5 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				38.89 
				 | 
			 
			
				| 
					 
						Granted (1) 
				 | 
				
					 
						  
				 | 
				0.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				54.97 
				 | 
			 
			
				| 
					 
						Vested 
				 | 
				
					 
						  
				 | 
				(0.2)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				35.69 
				 | 
			 
			
				| 
					 
						Forfeited 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				40.99 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				0.4 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				45.66 
				 | 
			 
		  
		
			
		 
		
 | 
			 
				 (1)
			 
		 | 
 | 
			 
			Performance shares granted assuming achievement of performance goals at target. Actual amount of shares to be earned may differ from this amount. 
 | 
 
  
		  
	   
 | 
| Other Information Pertaining to Performance Shares | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Year ended May 31, 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						2016 
				 | 
				
					 
						  
				 | 
				
					 
						2015 
				 | 
			 
			
				| 
					 
						Weighted-average grant-date fair value per share of performance shares granted 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				54.97 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				42.48 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				37.61 
				 | 
			 
			
				| 
					 
						Total grant-date fair value of performance shares vested 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				7.8 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				5.9 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				3.5 
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| Performance Stock Options [Member] | 
 
 | 
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | 
 
 | 
| Stock Option Activity | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Shares 
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
				
					 
						  
				 | 
				
					 
						remaining 
				 | 
				
					 
						  
				 | 
				
					 
						Aggregate 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						 subject 
				 | 
				
					 
						  
				 | 
				
					 
						exercise price 
				 | 
				
					 
						  
				 | 
				
					 
						contractual 
				 | 
				
					 
						  
				 | 
				
					 
						 intrinsic 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						to options 
				 | 
				
					 
						  
				 | 
				
					 
						per share 
				 | 
				
					 
						  
				 | 
				
					 
						term (years) 
				 | 
				
					 
						  
				 | 
				
					 
						value(1) 
				 | 
			 
			
				| 
					 
						Outstanding as of May 31, 2016 
				 | 
				
					 
						  
				 | 
				2.5 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				31.36 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Granted(2) 
				 | 
				
					 
						  
				 | 
				1.3 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				60.89 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Exercised 
				 | 
				
					 
						  
				 | 
				(0.4)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				30.65 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Forfeited 
				 | 
				
					 
						  
				 | 
				(1.0)
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				31.30 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Expired 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Outstanding as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				2.4 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				47.52 
				 | 
				
					 
						  
				 | 
				6.9 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				30.3 
				 | 
			 
			
				| 
					 
						Exercisable as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				1.1 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				31.69 
				 | 
				
					 
						  
				 | 
				4.3 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				30.3 
				 | 
			 
		  
		
			
		 
		
 | 
			 
				 (1)
			 
		 | 
 | 
			 
			Market price of the underlying stock as of May 31, 2017 less the exercise price. 
 | 
 
  
		
 | 
			 
				 (2)
			 
		 | 
 | 
			 
			LTIP performance stock options granted assumes achievement of performance goals at target.  Actual amount of shares to be earned may differ from this amount. 
 | 
 
  
		  
	   
 | 
| Other Information Pertaining to Stock Option | 
 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Year ended May 31, 
				 | 
			 
			
				| 
					 
						In millions 
				 | 
				
					 
						  
				 | 
				
					 
						2017 
				 | 
				
					 
						  
				 | 
				
					 
						2016 
				 | 
				
					 
						  
				 | 
				
					 
						2015 
				 | 
			 
			
				| 
					 
						Total intrinsic value of stock options exercised 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				12.4 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				1.0 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				2.7 
				 | 
			 
			
				| 
					 
						Total grant-date fair value of stock options vested 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				4.9 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				2.6 
				 | 
			 
		  
		
			
		 
		  
	   
 | 
| Performance-Based Restricted Stock [Member] | 
 
 | 
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | 
 
 | 
| Restricted Stock Activity | 
 
		
			
		 
		
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						Weighted- 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						average 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						grant-date 
				 | 
			 
			
				| 
					 
						 
				 | 
				
					 
						  
				 | 
				
					 
						Restricted 
				 | 
				
					 
						  
				 | 
				
					 
						fair value 
				 | 
			 
			
				| 
					 
						In millions, except per share amounts 
				 | 
				
					 
						  
				 | 
				
					 
						shares 
				 | 
				
					 
						  
				 | 
				
					 
						per share 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2016 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
			 
			
				| 
					 
						Granted(1) 
				 | 
				
					 
						  
				 | 
				0.2 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				53.74 
				 | 
			 
			
				| 
					 
						Vested 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
			 
			
				| 
					 
						Forfeited 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
			 
			
				| 
					 
						Nonvested as of May 31, 2017 
				 | 
				
					 
						  
				 | 
				0.2 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				53.74 
				 | 
			 
		  
		
 | 
			 
				 (1)
			 
		 | 
 | 
			 
			LTIP performance shares granted assumes achievement of performance goals at target.  Actual amount of shares to be earned may differ from this amount. 
 | 
 
  
		  
	   
 |