Fair Value Of Financial Instruments (Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) (Measured On A Recurring Basis [Member], USD $) | Sep. 30, 2013 | Dec. 31, 2012 |
In Thousands, unless otherwise specified |
Total Fair Value [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Total fair value of assets | $1,757,973 | $1,493,824 |
Total fair of value of liabilities | 21,230 | 11,968 |
Total Fair Value [Member] | Embedded Derivative Financial Instruments [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Derivative Financial Instruments, Liabilities, Fair Value Disclosure | 20,926 | 11,203 |
Total Fair Value [Member] | Money Market Funds [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments in money market funds | 13,435 | 38,054 |
Total Fair Value [Member] | Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | 1,744,223 | 1,452,358 |
Total Fair Value [Member] | Equity Securities [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | | 3,341 |
Total Fair Value [Member] | Forward Contracts [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Foreign currency forward contracts assets | 315 | 71 |
Foreign currency forward contracts liabilities | 304 | 765 |
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Total fair value of assets | 1,757,658 | 1,457,334 |
Total fair of value of liabilities | 0 | 0 |
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Embedded Derivative Financial Instruments [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Derivative Financial Instruments, Liabilities, Fair Value Disclosure | 0 | 0 |
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Money Market Funds [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments in money market funds | 13,435 | 38,054 |
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | 1,744,223 | 1,419,280 |
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Equity Securities [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | | 0 |
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Forward Contracts [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Foreign currency forward contracts assets | 0 | 0 |
Foreign currency forward contracts liabilities | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Total fair value of assets | 315 | 36,490 |
Total fair of value of liabilities | 304 | 765 |
Significant Other Observable Inputs (Level 2) [Member] | Embedded Derivative Financial Instruments [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Derivative Financial Instruments, Liabilities, Fair Value Disclosure | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments in money market funds | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | 0 | 33,078 |
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | | 3,341 |
Significant Other Observable Inputs (Level 2) [Member] | Forward Contracts [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Foreign currency forward contracts assets | 315 | 71 |
Foreign currency forward contracts liabilities | 304 | 765 |
Significant Unobservable Inputs (Level 3) [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Total fair value of assets | 0 | 0 |
Total fair of value of liabilities | 20,926 | 11,203 |
Significant Unobservable Inputs (Level 3) [Member] | Embedded Derivative Financial Instruments [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Derivative Financial Instruments, Liabilities, Fair Value Disclosure | 20,926 | 11,203 |
Significant Unobservable Inputs (Level 3) [Member] | Money Market Funds [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments in money market funds | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Forward Contracts [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Foreign currency forward contracts assets | 0 | 0 |
Foreign currency forward contracts liabilities | $0 | $0 |