Consolidated Statements of Income and Comprehensive Income (Unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Revenue:
Service revenue	$ 626.0	$ 582.4	$ 1,824.4	$ 1,709.9
Interest on funds held for clients	10.5	10.9	30.5	31.0
Total revenue	636.5	593.3	1,854.9	1,740.9
Expenses:
Operating expenses	177.1	171.2	509.5	498.3
Selling, general and administrative expenses	208.7	197.1	591.0	549.6
Total expenses	385.8	368.3	1,100.5	1,047.9
Operating income	250.7	225.0	754.4	693.0
Investment income, net	1.5	1.4	4.0	5.2
Income before income taxes	252.2	226.4	758.4	698.2
Income taxes	92.1	81.9	276.8	252.7
Net income	160.1	144.5	481.6	445.5
Other comprehensive income/(loss), net of tax:
Unrealized gains/(losses) on securities, net of tax	10.9	(7.0)	2.6	(5.0)
Total other comprehensive income/(loss), net of tax	10.9	(7.0)	2.6	(5.0)
Comprehensive income	$ 171.0	$ 137.5	$ 484.2	$ 440.5
Basic earnings per share	$ 0.44	$ 0.40	$ 1.32	$ 1.23
Diluted earnings per share	$ 0.44	$ 0.40	$ 1.31	$ 1.22
Weighted-average common shares outstanding	364.2	363.8	364.8	363.5
Weighted-average common shares outstanding, assuming dilution	365.8	364.6	366.3	364.2
Cash dividends per common share	$ 0.35	$ 0.66	$ 1.05	$ 1.31