Fair Value Of Financial Instruments (Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) - Measured On A Recurring Basis [Member] - USD ($) $ in Thousands | Sep. 30, 2015 | Dec. 31, 2014 |
Total Fair Value [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Total fair value of assets | $ 1,826,594 | $ 1,318,859 |
Total fair of value of liabilities | 25,187 | 26,924 |
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 | 25,054 | 26,755 |
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 | 113,223 | 85,453 |
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 | 1,712,986 | 1,233,076 |
Total Fair Value [Member] | Equity Securities [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Investments, Fair Value Disclosure | 101 | |
Total Fair Value [Member] | Forward Contracts [Member] | | |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | | |
Foreign currency forward contracts assets | 284 | 330 |
Foreign currency forward contracts liabilities | 133 | 169 |
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 | 1,826,310 | 1,318,529 |
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 | 113,223 | 85,453 |
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 | 1,712,986 | 1,233,076 |
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 | 101 | |
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 | 284 | 330 |
Total fair of value of liabilities | 133 | 169 |
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 | 0 |
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 | 0 | |
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 | 284 | 330 |
Foreign currency forward contracts liabilities | 133 | 169 |
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 | 25,054 | 26,755 |
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 | 25,054 | 26,755 |
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 |