Interim Financial Data By Segment (Financial Data By Strategic Business Unit Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 2,923.1	$ 2,737.3	$ 8,028.6	$ 7,372.4
Earnings before Income Taxes	685.6	653.0	1,724.6	1,574.0
Employer Services [Member]
Segment Reporting Information [Line Items]
Revenues	2,108.6	1,973.5	5,686.1	5,280.0
Earnings before Income Taxes	699.4	653.7	1,556.4	1,474.1
PEO Services [Member]
Segment Reporting Information [Line Items]
Revenues	513.7	447.8	1,328.1	1,147.3
Earnings before Income Taxes	45.9	37.8	124.8	101.8
Dealer Services [Member]
Segment Reporting Information [Line Items]
Revenues	431.9	402.0	1,252.3	1,134.2
Earnings before Income Taxes	77.7	67.4	211.3	174.6
Other [Member]
Segment Reporting Information [Line Items]
Revenues	0.9	3.7	4.9	10.1
Earnings before Income Taxes	(62.0)	(57.4)	(48.1)	(111.1)
Foreign Exchange [Member]
Segment Reporting Information [Line Items]
Revenues	(23.9)	(10.8)	(29.0)	(56.0)
Earnings before Income Taxes	(0.5)	0.1	0.2	(7.6)
Client Fund Interest [Member]
Segment Reporting Information [Line Items]
Revenues	(108.1)	(78.9)	(213.8)	(143.2)
Earnings before Income Taxes	(108.1)	(78.9)	(213.8)	(143.2)
Cost Of Capital Charge [Member]
Segment Reporting Information [Line Items]
Earnings before Income Taxes	$ 33.2	$ 30.3	$ 93.8	$ 85.4