Annual report pursuant to Section 13 and 15(d)

Funds Held for Clients and Corporate Investments (Realized Gains and Losses from Sale of Available-for-sale Securities) (Details)

v3.5.0.2
Funds Held for Clients and Corporate Investments (Realized Gains and Losses from Sale of Available-for-sale Securities) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Feb. 29, 2016
 [1]
May 31, 2015
 [1]
Nov. 30, 2014
 [1]
Aug. 31, 2014
 [1]
May 31, 2016
May 31, 2015
May 31, 2014
Funds Held for Clients and Corporate Investments [Abstract]              
Gross realized gains         $ 0.1 $ 0.3 $ 0.6
Gross realized losses        
Net realized gains $ 0.1 $ 0.1 $ 0.1 $ 0.1 $ 0.1 [1] $ 0.3 [1] $ 0.6
[1] Total net realized gains on the combined funds held for clients and corporate investment portfolios.