Fair Value Of Financial Instruments (Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) (Measured On A Recurring Basis [Member], USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
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 | $1,476,742 | $1,655,695 |
Total fair of value of liabilities | 18,589 | 29,135 |
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 | 18,489 | 29,004 |
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 | 168,508 | 246,492 |
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 | 1,308,110 | 1,409,062 |
Total Fair Value [Member] | Forward Contracts [Member] | ' | ' |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | ' | ' |
Foreign currency forward contracts assets | 124 | 141 |
Foreign currency forward contracts liabilities | 100 | 131 |
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 | 1,476,618 | 1,655,554 |
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 | 168,508 | 246,492 |
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 | 1,308,110 | 1,409,062 |
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 | 124 | 141 |
Total fair of value of liabilities | 100 | 131 |
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] | Forward Contracts [Member] | ' | ' |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | ' | ' |
Foreign currency forward contracts assets | 124 | 141 |
Foreign currency forward contracts liabilities | 100 | 131 |
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 | 18,489 | 29,004 |
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 | 18,489 | 29,004 |
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] | 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 |