Summary of Significant Accounting Policies (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									12 Months Ended
	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares		Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2016 USD ($) d $ / shares shares	Jun. 30, 2015 USD ($) business $ / shares shares		Jun. 30, 2014 USD ($) $ / shares shares		Jun. 30, 2013 USD ($)
Property, Plant and Equipment [Line Items]
Operating Leases, Rent Expense										$ 271.3	$ 237.9		$ 227.4
Number of businesses acquired | business											1
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	$ 1,682.0				$ 1,793.5	[1]				$ 1,682.0	$ 1,793.5	[1]	1,883.5	[1]
Goodwill, Impairment Loss											42.7
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	$ 282.0	$ 532.5	$ 341.4	$ 337.5	$ 257.0		$ 490.3	$ 332.5	$ 296.6	$ 1,493.4	$ 1,376.5		$ 1,242.6
Weighted Average Number of Shares Outstanding, Basic | shares										457.0	472.6		478.9
Incremental Common Shares Attributable to Call Options and Warrants | shares										0.8	1.6		2.7
Effect of Employee Restricted stock Shares On Weighted Average Number of Diluted Shares Outstanding | shares										1.3	1.6		1.5
Weighted Average Number of Shares Outstanding, Diluted | shares										459.1	475.8		483.1
Options excluded from the calculation of diluted earnings per share because their exercise prices exceeded the average market price | shares										1.8	0.4		1.5
Basic Earnings Per Share from Continuing Operations | $ / shares	$ 0.62	$ 1.17	$ 0.75	$ 0.73	$ 0.55		$ 1.04	$ 0.70	$ 0.62	$ 3.27	$ 2.91		$ 2.59
Diluted earnings per share from continuing operations | $ / shares	$ 0.62	$ 1.17	$ 0.74	$ 0.72	$ 0.55		$ 1.03	$ 0.69	$ 0.62	$ 3.25	$ 2.89		$ 2.57
Unrecognized Tax Benefits	$ 27.4				$ 27.1					$ 27.4	$ 27.1		$ 56.5		$ 67.0
Tax Settlements Future Impact Potential On Earnings Maximum										$ 2.0
Debt Instrument, Issuance Date									Sep. 08, 2015
Debt Instrument, Face Amount									$ 2,000.0
Business Combination, Consideration Transferred											$ 10.1
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										4 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 and 2014 is net of accumulated impairment losses of $42.7 million related to the Employer Services segment.