Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	$ 835.9	$ 925.7
Other marketable securities	163.7	213.6
Derivative financial instruments - Assets	0.1	0.2
Total Assets	999.7	1,139.5
Loan related to other marketable securities	163.7	213.6
Derivative financial instruments - Liabilities	0.2	1.0
Total Liabilities	163.9	214.6
U.S. Government Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	165.3	258.4
Corporate Debt Obligations Guaranteed By FDIC [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	72.1	102.6
Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	224.5	95.9
Foreign Corporate Debt Obligations Guaranteed By Foreign Governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	86.4	88.3
Mortgage-Backed Debt Obligations Guaranteed By GNMA [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	94.9	175.1
Certificates Of Deposit Guaranteed By FDIC [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	2.0	3.3
Foreign Government Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	190.7	202.1
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	165.3	258.4
Other marketable securities	163.7	213.6
Total Assets	329.0	472.0
Loan related to other marketable securities	163.7	213.6
Total Liabilities	163.9	213.6
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | U.S. Government Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	165.3	258.4
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	670.6	667.3
Derivative financial instruments - Assets	0.1	0.2
Total Assets	670.7	667.5
Derivative financial instruments - Liabilities	0.2	1.0
Total Liabilities	0.2	1.0
Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt Obligations Guaranteed By FDIC [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	72.1	102.6
Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	224.5	95.9
Significant Other Observable Inputs (Level 2) [Member] | Foreign Corporate Debt Obligations Guaranteed By Foreign Governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	86.4	88.3
Significant Other Observable Inputs (Level 2) [Member] | Mortgage-Backed Debt Obligations Guaranteed By GNMA [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	94.9	175.1
Significant Other Observable Inputs (Level 2) [Member] | Certificates Of Deposit Guaranteed By FDIC [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	2.0	3.3
Significant Other Observable Inputs (Level 2) [Member] | Foreign Government Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities	190.7	202.1
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Other marketable securities
Derivative financial instruments - Assets
Total Assets
Loan related to other marketable securities
Derivative financial instruments - Liabilities
Total Liabilities
Significant Unobservable Inputs (Level 3) [Member] | U.S. Government Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Significant Unobservable Inputs (Level 3) [Member] | Corporate Debt Obligations Guaranteed By FDIC [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Significant Unobservable Inputs (Level 3) [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Significant Unobservable Inputs (Level 3) [Member] | Foreign Corporate Debt Obligations Guaranteed By Foreign Governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Significant Unobservable Inputs (Level 3) [Member] | Mortgage-Backed Debt Obligations Guaranteed By GNMA [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Significant Unobservable Inputs (Level 3) [Member] | Certificates Of Deposit Guaranteed By FDIC [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities
Significant Unobservable Inputs (Level 3) [Member] | Foreign Government Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Investments in marketable securities