Interim Financial Data By Segment (Financial Data By Strategic Business Unit Segment) (Details) (USD $) In Millions	3 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Revenues	$ 2,522.5	$ 2,229.4
Earnings before Income Taxes	459.3	436.4
Employer Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	1,750.4	1,599.3
Earnings before Income Taxes	410.0	382.4
Professional Employee Organization Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	400.5	341.3
Earnings before Income Taxes	36.6	28.0
Dealer Services Segment [Member]
Segment Reporting Information [Line Items]
Revenues	407.9	346.2
Earnings before Income Taxes	63.1	49.6
Other Reportable Segment [Member]
Segment Reporting Information [Line Items]
Revenues	2.8	3.3
Earnings before Income Taxes	(33.1)	(18.3)
Foreign Exchange Reconciling Item [Member]
Segment Reporting Information [Line Items]
Revenues	9.7	(32.6)
Earnings before Income Taxes	0.7	(3.2)
Client Fund Interest Reconciling Item [Member]
Segment Reporting Information [Line Items]
Revenues	(48.8)	(28.1)
Earnings before Income Taxes	(48.8)	(28.1)
Cost Of Capital Charge Reconciling Item [Member]
Segment Reporting Information [Line Items]
Earnings before Income Taxes	30.8	26.0
Total Revenue And Earnings Before Income Taxes [Member]
Segment Reporting Information [Line Items]
Revenues	2,522.5	2,229.4
Earnings before Income Taxes	$ 459.3	$ 436.4

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph h

-Subparagraph 1(i)

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

+ Details

Name:	us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 1

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration