Financial Data By Segment (Financial Data By Strategic Business Unit Segment) (Details) $ in Millions	3 Months Ended															12 Months Ended
	Jun. 30, 2017 USD ($)		Mar. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		Sep. 30, 2016 USD ($)		Jun. 30, 2016 USD ($)		Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)		Sep. 30, 2015 USD ($)		Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)
Segment Reporting Information [Line Items]
Revenues	$ 3,064.8		$ 3,410.8		$ 2,987.3		$ 2,916.9		$ 2,898.2		$ 3,248.6	$ 2,807.0		$ 2,714.0		$ 12,379.8	$ 11,667.8	$ 10,938.5
Earnings from Continuing Operations before Income Taxes	388.4	[1]	$ 827.9	[2]	$ 786.2	[3]	$ 528.7	[4]	427.0	[5]	$ 794.8	$ 507.9	[6]	$ 505.0	[7]	2,531.1	2,234.7	2,070.7
Assets from Continuing Operations	37,180.0								43,670.0							37,180.0	43,670.0	33,110.5
Capital Expenditures from continuing operations																249.0	165.7	171.2
Depreciation, Depletion and Amortization																$ 316.1	288.6	277.9
Number of Reportable Segments | segment																2
Standard Reconciling Rate Between Actual Interest Income Earned And Interest Credited																4.50%
Employer Services [Member]
Segment Reporting Information [Line Items]
Revenues																$ 9,535.2	9,211.9	8,815.1
Earnings from Continuing Operations before Income Taxes																2,921.3	2,800.4	2,595.4
Assets from Continuing Operations	30,107.7								36,637.5							30,107.7	36,637.5	27,507.3
Capital Expenditures from continuing operations																83.0	71.1	94.8
Depreciation, Depletion and Amortization																247.3	230.7	221.2
PEO Services [Member]
Segment Reporting Information [Line Items]
Revenues																3,483.6	3,073.1	2,647.2
Earnings from Continuing Operations before Income Taxes																448.6	371.2	301.8
Assets from Continuing Operations	586.8								534.6							586.8	534.6	377.7
Capital Expenditures from continuing operations																0.2	1.0	1.3
Depreciation, Depletion and Amortization																1.3	1.5	1.2
Other [Member]
Segment Reporting Information [Line Items]
Revenues																(10.6)	1.9	69.8
Earnings from Continuing Operations before Income Taxes																(210.4)	(317.8)	(232.9)
Assets from Continuing Operations	6,485.5								6,497.9							6,485.5	6,497.9	5,225.5
Capital Expenditures from continuing operations																165.8	93.6	75.1
Depreciation, Depletion and Amortization																67.5	56.4	55.5
Client Fund Interest [Member]
Segment Reporting Information [Line Items]
Revenues																(628.4)	(619.1)	(593.6)
Earnings from Continuing Operations before Income Taxes																(628.4)	(619.1)	(593.6)
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

[1] Earnings from continuing operations before income taxes; net earnings from continuing operations; and basic and diluted EPS from continuing operations include charges for the Workforce Optimization Effort and Service Alignment Initiative. The combined impact decreased earnings from continuing operations before income taxes by $43.5 million and, net earnings from continuing operations and net earnings by $27.1 million and basic and diluted earnings per share from continuing operations by $0.06.

[2] Earnings from continuing operations before income taxes; net earnings from continuing operations; and basic and diluted EPS from continuing operations include charges for the Service Alignment Initiative. This decreased earnings from continuing operations before income taxes by $0.6 million, and net earnings from continuing operations and net earnings by $0.4 million, and had no impact on basic and diluted earnings per share from continuing operations.

[3] Earnings from continuing operations before income taxes; net earnings from continuing operations; and basic and diluted EPS from continuing operations include the gain on the sale of the COBRA and CHSA businesses. This increased earnings from continuing operations before income taxes by $205.4 million, net earnings from continuing operations and net earnings by $121.4 million, and basic and diluted earnings per share from continuing operations by $0.27.

[4] Earnings from continuing operations before income taxes; net earnings from continuing operations; and basic and diluted EPS from continuing operations include the charge for the Service Alignment Initiative. This decreased earnings from continuing operations before income taxes by $39.9 million, net earnings from continuing operations by $24.8 million and basic and diluted earnings per share from continuing operations by $0.05.

[5] Earnings from continuing operations before income taxes; net earnings from continuing operations; net earnings; and basic and diluted EPS from continuing operations include the charge for the Workforce Optimization Effort. This decreased earnings from continuing operations before income taxes by $48.2 million net earnings from continuing operations and net earnings by $31.8 million and basic and diluted earnings per share from continuing operations by $0.07.

[6] Earnings from continuing operations before income taxes; net earnings from continuing operations; net earnings; and basic and diluted EPS from continuing operations include the gain on sale of a building. This increased earnings from continuing operations before income taxes by $13.9 million net earnings from continuing operations and net earnings by $8.6 million and basic and diluted earnings per share from continuing operations by $0.02.

[7] Earnings from continuing operations before income taxes; net earnings from continuing operations; net earnings; and basic and diluted EPS from continuing operations include the gain on the sale of AMD. This increased earnings from continuing operations before income taxes by $29.1 million, net earnings from continuing operations and net earnings by $21.8 million, and basic and diluted earnings per share from continuing operations by $0.05