Fair Value Measurements (Schedule Of Assets Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Jun. 30, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	$ 17,149.4	$ 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	18.8	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	17,130.6	16,907.4
Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	17,149.4	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	6,810.6	6,759.1
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	6,810.6	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	6,483.9	6,126.6
Corporate Bonds [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	6,483.9	6,126.6
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	376.7	447.8
Asset-Backed Securities [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	376.7	447.8
Commercial Mortgage-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	388.0	492.5
Commercial Mortgage-Backed Securities [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	388.0	492.5
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	528.1	516.2
Municipal Bonds [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	528.1	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	1,027.5	1,101.5
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	1,027.5	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	18.8	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	1,515.8	1,463.7
Other Securities [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	1,534.6	1,483.8
Corporate Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	122.6	134.3
Funds Held For Clients [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total available-for-sale securities - Fair Value	$ 17,026.8	$ 16,793.2