Interim Financial Data By Segment (Financial Data By Strategic Business Unit Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 2,747.8	$ 2,570.7	$ 5,385.3	$ 5,081.6
Earnings from Continuing Operations before Income Taxes	528.8	576.2	994.4	1,031.9
Employer Services [Member]
Segment Reporting Information [Line Items]
Revenues	1,907.7	1,782.0	3,726.7	3,490.9
Earnings from Continuing Operations before Income Taxes	485.0	441.0	906.8	848.2
PEO Services [Member]
Segment Reporting Information [Line Items]
Revenues	465.7	413.8	917.6	814.4
Earnings from Continuing Operations before Income Taxes	49.8	42.5	96.0	79.1
Dealer Services [Member]
Segment Reporting Information [Line Items]
Revenues	449.8	406.9	889.6	809.5
Earnings from Continuing Operations before Income Taxes	86.2	70.7	162.2	134.1
Other [Member]
Segment Reporting Information [Line Items]
Revenues	0.4	1.5	1.2	4.2
Earnings from Continuing Operations before Income Taxes	(33.6)	50.6	(67.6)	19.8
Foreign Exchange [Member]
Segment Reporting Information [Line Items]
Revenues	13.3	23.5	13.4	68.3
Earnings from Continuing Operations before Income Taxes	2.0	0.6	3.2	(0.1)
Client Fund Interest [Member]
Segment Reporting Information [Line Items]
Revenues	(89.1)	(57.0)	(163.2)	(105.7)
Earnings from Continuing Operations before Income Taxes	(89.1)	(57.0)	(163.2)	(105.7)
Cost Of Capital Charge [Member]
Segment Reporting Information [Line Items]
Earnings from Continuing Operations before Income Taxes	$ 28.5	$ 27.8	$ 57.0	$ 56.5