Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Data (Quarterly Financial Data) (Details)

v3.10.0.1
Quarterly Financial Data (Quarterly Financial Data) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended 12 Months Ended
May 31, 2018
Feb. 28, 2018
Nov. 30, 2017
Aug. 31, 2017
May 31, 2017
Feb. 28, 2017
Nov. 30, 2016
Aug. 31, 2016
May 31, 2018
May 31, 2017
May 31, 2016
Quarterly Financial Data [Abstract]                      
Service revenue $ 853.4 $ 848.4 $ 812.5 $ 803.1 $ 784.6 $ 782.6 $ 760.0 $ 773.5 $ 3,317.4 $ 3,100.7 $ 2,905.8
Interest on funds held for clients 17.7 18.1 14.0 13.7 14.0 13.2 11.4 12.0 63.5 50.6 46.1
Total revenue 871.1 866.5 826.5 816.8 798.6 795.8 771.4 785.5 3,380.9 3,151.3 2,951.9
Operating income 317.8 292.5 332.2 345.0 298.9 306.6 311.1 323.0 1,287.5 1,239.6 1,146.6
Investment income, net 2.5 2.3 1.7 2.1 1.6 1.2 0.9 1.5 8.6 5.2 4.5
Income before income taxes 320.3 294.8 333.9 347.1 300.5 307.8 312.0 324.5 1,296.1 1,244.8 1,151.1
Income taxes 91.8 [1] 34.4 [1] 116.9 [1] 119.3 [1] 105.2 105.3 109.9 107.1 362.4 [1] 427.5 394.3
Net income $ 228.5 $ 260.4 $ 217.0 $ 227.8 $ 195.3 $ 202.5 $ 202.1 $ 217.4 $ 933.7 $ 817.3 $ 756.8
Basic earnings per share $ 0.64 [2] $ 0.72 [2] $ 0.60 [2] $ 0.63 [2] $ 0.54 [2] $ 0.56 [2] $ 0.56 [2] $ 0.60 [2] $ 2.60 [2] $ 2.27 [2] $ 2.10
Diluted earnings per share $ 0.63 [2] $ 0.72 [2] $ 0.60 [2] $ 0.63 [2] $ 0.54 [2] $ 0.56 [2] $ 0.56 [2] $ 0.60 [2] $ 2.58 [2] $ 2.25 [2] $ 2.09
Weighted-average common shares outstanding 359.0 359.2 359.1 358.9 359.3 359.0 360.2 361.0 359.0 359.8 360.7
Weighted-average common shares outstanding, assuming dilution 361.5 362.0 361.4 361.3 362.1 361.8 362.6 364.1 361.5 362.6 362.5
Cash dividends per common share $ 0.56 $ 0.50 $ 0.50 $ 0.50 $ 0.46 $ 0.46 $ 0.46 $ 0.46 $ 2.06 $ 1.84 $ 1.68
Total net realized gains   $ 0.1 [3]           $ 0.1 [3] $ 0.1 [3] $ 0.1 [3] $ 0.1
[1] As a result of the Tax Act, the effective income tax rate for the three months ended February 28, 2018 was significantly impacted by certain one-time net tax benefits. Refer to Note K for further details.
[2] Each quarter is a discrete period and the sum of the four quarters' basic and diluted earnings per share amounts may not equal the full year amount.
[3] Total net realized gains on the combined funds held for clients and corporate investment portfolios.