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, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 3,114.3	$ 2,910.9	$ 8,499.6	$ 7,992.4
Earnings from Continuing Operations before Income Taxes	724.8	682.1	1,719.2	1,714.0
Employer Services [Member]
Segment Reporting Information [Line Items]
Revenues	2,212.6	2,061.8	5,939.3	5,552.7
Earnings from Continuing Operations before Income Taxes	762.4	691.3	1,669.3	1,539.6
PEO Services [Member]
Segment Reporting Information [Line Items]
Revenues	565.5	513.7	1,483.1	1,328.1
Earnings from Continuing Operations before Income Taxes	54.5	46.0	150.5	125.2
Dealer Services [Member]
Segment Reporting Information [Line Items]
Revenues	460.5	426.2	1,350.1	1,235.7
Earnings from Continuing Operations before Income Taxes	88.0	77.8	250.2	211.9
Other [Member]
Segment Reporting Information [Line Items]
Revenues	0.2	0.8	1.4	4.9
Earnings from Continuing Operations before Income Taxes	(68.5)	(57.9)	(136.2)	(38.3)
Foreign Exchange [Member]
Segment Reporting Information [Line Items]
Revenues	18.4	16.4	31.8	84.7
Earnings from Continuing Operations before Income Taxes	3.2	1.1	6.4	1.0
Client Fund Interest [Member]
Segment Reporting Information [Line Items]
Revenues	(142.9)	(108.0)	(306.1)	(213.7)
Earnings from Continuing Operations before Income Taxes	(142.9)	(108.0)	(306.1)	(213.7)
Cost Of Capital Charge [Member]
Segment Reporting Information [Line Items]
Earnings from Continuing Operations before Income Taxes	$ 28.1	$ 31.8	$ 85.1	$ 88.3