Financial Data By Segment (Financial Data By Strategic Business Unit Segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenues	$ 2,898.2	$ 3,248.6	$ 2,807.0	$ 2,714.0	$ 2,694.5	$ 3,024.3	$ 2,653.6	$ 2,566.1	$ 11,667.8	$ 10,938.5	$ 10,226.4
Earnings from Continuing Operations before Income Taxes	427.0	$ 794.8	$ 507.9	$ 505.0	381.6	$ 739.9	$ 498.8	$ 450.4	2,234.7	2,070.7	1,879.2
Assets from Continuing Operations	43,670.0				33,110.5				43,670.0	33,110.5	29,629.6
Capital Expenditures from continuing operations									165.7	171.2	161.0
Depreciation, Depletion and Amortization									$ 288.6	277.9	266.6
Number of Reportable Segments									2
Standard Reconciling Rate Between Actual Interest Income Earned And Interest Credited									4.50%
Employer Services [Member]
Segment Reporting Information [Line Items]
Revenues									$ 9,211.9	8,815.1	8,437.6
Earnings from Continuing Operations before Income Taxes									2,867.9	2,693.0	2,521.2
Assets from Continuing Operations	36,637.5				27,507.3				36,637.5	27,507.3	21,684.9
Capital Expenditures from continuing operations									71.1	94.8	90.4
Depreciation, Depletion and Amortization									230.7	221.2	211.0
PEO Services [Member]
Segment Reporting Information [Line Items]
Revenues									3,073.1	2,647.2	2,270.9
Earnings from Continuing Operations before Income Taxes									371.7	302.8	233.6
Assets from Continuing Operations	534.6				377.7				534.6	377.7	472.6
Capital Expenditures from continuing operations									1.0	1.3	0.9
Depreciation, Depletion and Amortization									1.5	1.2	1.2
Other [Member]
Segment Reporting Information [Line Items]
Revenues									1.9	69.8	67.5
Earnings from Continuing Operations before Income Taxes									(385.8)	(331.5)	(326.0)
Assets from Continuing Operations	6,497.9				5,225.5				6,497.9	5,225.5	7,472.1
Capital Expenditures from continuing operations									93.6	75.1	69.7
Depreciation, Depletion and Amortization									56.4	55.5	54.4
Client Fund Interest [Member]
Segment Reporting Information [Line Items]
Revenues									(619.1)	(593.6)	(549.6)
Earnings from Continuing Operations before Income Taxes									(619.1)	(593.6)	(549.6)
Assets from Continuing Operations	$ 0.0				$ 0.0				0.0	0.0	0.0
Capital Expenditures from continuing operations									0.0	0.0	0.0
Depreciation, Depletion and Amortization									$ 0.0	$ 0.0	$ 0.0