Summary of Significant Accounting Policies (Details) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended								12 Months Ended
		Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares	Sep. 30, 2013 USD ($) $ / shares	Jun. 30, 2015 USD ($) business d $ / shares shares	Jun. 30, 2014 USD ($) business $ / shares shares	Jun. 30, 2013 USD ($) $ / shares shares	Jun. 30, 2012 USD ($)
Property, Plant and Equipment [Line Items]
Operating Leases, Rent Expense										$ 237.9	$ 227.4	$ 209.6
Number of businesses acquired | business										1	2
Business Combination, Consideration Transferred										$ 10.1	$ 40.4
Percent of Level Two Investment Pricing Inputs Provided by Independent Pricing Service		99.00%								99.00%
Minimum days receivable considered delinquent | d										30
Financing Receivable, Nonaccrual Status, Minimum Number of Days Past Due | d										60
Number of days to resume interest revenue recognition | d										60
Goodwill	[1]	$ 1,793.5				$ 1,883.5				$ 1,793.5	1,883.5	1,866.4
Goodwill, Impairment Loss										0.0	0.0	42.7
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest		$ 257.0	$ 490.3	$ 332.5	$ 296.6	$ 233.2	$ 432.1	$ 313.2	$ 264.2	$ 1,376.5	$ 1,242.6	$ 1,122.2
Weighted Average Number of Shares Outstanding, Basic | shares										472.6	478.9	482.7
Incremental Common Shares Attributable to Call Options and Warrants | shares										1.6	2.7	3.3
Effect of Employee Restricted stock Shares On Weighted Average Number of Diluted Shares Outstanding | shares										1.6	1.5	1.1
Weighted Average Number of Shares Outstanding, Diluted | shares										475.8	483.1	487.1
Options excluded from the calculation of diluted earnings per share because their exercise prices exceeded the average market price | shares										0.4	1.5	1.2
Basic Earnings Per Share from Continuing Operations | $ / shares		$ 0.55	$ 1.04	$ 0.70	$ 0.62	$ 0.49	$ 0.90	$ 0.65	$ 0.55	$ 2.91	$ 2.59	$ 2.32
Diluted earnings per share from continuing operations | $ / shares		$ 0.55	$ 1.03	$ 0.69	$ 0.62	$ 0.48	$ 0.89	$ 0.65	$ 0.55	$ 2.89	$ 2.57	$ 2.30
Unrecognized Tax Benefits		$ 27.1				$ 56.5				$ 27.1	$ 56.5	$ 67.0	$ 79.2
Tax Settlements Future Impact Potential On Earnings Maximum										5.0
Reinsurance Recoverables		1.0								1.0
Worker's Compensation per occurrence reinsurance		$ 1.0								$ 1.0
Computer software to be marketed and sold										3 years
Minimum [Member]
Property, Plant and Equipment [Line Items]
Internal Use Software Life of Asset										3 years
Minimum [Member] | Data Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life										2 years
Minimum [Member] | Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life										20 years
Minimum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life										3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Internal Use Software Life of Asset										5 years
Maximum [Member] | Data Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life										5 years
Maximum [Member] | Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life										40 years
Maximum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment Useful Life										7 years

[1] The goodwill balance at June 30, 2015, 2014, and 2013 is net of accumulated impairment losses of $42.7 million related to the Employer Services segment.