Financial Data By Segment (Financial Data By Strategic Business Unit Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information [Line Items]
Revenues	$ 2,810.5	$ 3,114.3	$ 2,747.8	$ 2,637.5	$ 2,623.6	$ 2,910.9	$ 2,570.7	$ 2,510.9	$ 11,310.1	$ 10,616.0	$ 9,833.0
Earnings from Continuing Operations before Income Taxes									2,084.3	2,107.9	1,918.0
Assets	32,268.1				30,817.4				32,268.1	30,817.4	34,112.3
Assets from Continuing Operations					30,692.4					30,692.4
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									174.8	146.2	184.8
Depreciation, Depletion and Amortization									317.0	319.7	314.6
Employer Services [Member]
Segment Reporting Information [Line Items]
Revenues									7,914.0	7,388.5	6,878.3
Earnings from Continuing Operations before Income Taxes									2,134.2	1,949.2	1,831.9
Assets	24,174.9				23,326.8				24,174.9	23,326.8	27,034.4
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									57.9	39.9	51.3
Depreciation, Depletion and Amortization									212.3	209.0	201.6
PEO Services [Member]
Segment Reporting Information [Line Items]
Revenues									1,973.2	1,771.4	1,543.9
Earnings from Continuing Operations before Income Taxes									199.2	170.6	137.3
Assets	411.4				376.5				411.4	376.5	262.1
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									0.6	1.2	1.2
Depreciation, Depletion and Amortization									1.4	1.2	1.1
Dealer Services [Member]
Segment Reporting Information [Line Items]
Revenues									1,813.7	1,661.3	1,513.5
Earnings from Continuing Operations before Income Taxes									335.7	277.6	231.3
Assets	696.8				685.9				696.8	685.9	677.4
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									35.1	39.7	34.4
Depreciation, Depletion and Amortization									97.0	99.9	99.3
Other [Member]
Segment Reporting Information [Line Items]
Revenues									1.7	5.5	12.9
Earnings from Continuing Operations before Income Taxes									(272.8)	(102.0)	(178.1)
Assets	6,985.0				6,303.2				6,985.0	6,303.2	6,138.4
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									81.2	65.4	97.9
Depreciation, Depletion and Amortization									119.3	126.1	122.0
Foreign Exchange [Member]
Segment Reporting Information [Line Items]
Revenues									39.9	96.4	97.2
Earnings from Continuing Operations before Income Taxes									7.4	3.1	(1.0)
Assets	0				0				0	0	0
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									0	0	0
Depreciation, Depletion and Amortization									0	0	0
Client Fund Interest [Member]
Segment Reporting Information [Line Items]
Revenues									(432.4)	(307.1)	(212.8)
Earnings from Continuing Operations before Income Taxes									(432.4)	(307.1)	(212.8)
Assets	0				0				0	0	0
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									0	0	0
Depreciation, Depletion and Amortization									0	0	0
Cost Of Capital Charge [Member]
Segment Reporting Information [Line Items]
Revenues									0	0	0
Earnings from Continuing Operations before Income Taxes									113.0	116.5	109.4
Assets	0				0				0	0	0
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets									0	0	0
Depreciation, Depletion and Amortization									$ (113.0)	$ (116.5)	$ (109.4)