Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Jun. 30, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	$ 18,093.4	$ 16,927.5
Percent of Level Two Investment Pricing Inputs Provided by Pricing Service	99.00%
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	20.6	20.1
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	18,072.8	16,907.4
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	18,093.4	16,927.5
U.S. Treasury And Direct Obligations Of U.S. Government Agencies [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	6,674.6	6,759.1
U.S. Treasury And Direct Obligations Of U.S. Government Agencies [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
U.S. Treasury And Direct Obligations Of U.S. Government Agencies [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	6,674.6	6,759.1
Corporate Bonds [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	7,368.0	6,126.6
Corporate Bonds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Corporate Bonds [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	7,368.0	6,126.6
Canadian Provincial Bonds [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	655.9	494.3
Canadian Provincial Bonds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Canadian Provincial Bonds [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	655.9	494.3
Asset-Backed Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	548.4	447.8
Asset-Backed Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Asset-Backed Securities [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	548.4	447.8
Municipal Bonds [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	552.9	516.2
Municipal Bonds [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Municipal Bonds [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	552.9	516.2
Canadian Government Obligations And Canadian Government Agency Obligations [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	1,017.0	1,101.5
Canadian Government Obligations And Canadian Government Agency Obligations [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Canadian Government Obligations And Canadian Government Agency Obligations [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	1,017.0	1,101.5
Other Securities [Member] \| Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	20.6	20.1
Other Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	1,256.0	1,461.9
Other Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value
Other Securities [Member] \| Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	1,276.6	1,482.0
Corporate Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	117.3	134.3
Funds Held For Clients [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	$ 17,976.1	$ 16,793.2

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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