Fair Value Of Financial Instruments (Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 29,004	$ 11,203
Measured On A Recurring Basis [Member] | Total Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total fair value of assets	1,655,695	1,493,824
Total fair of value of liabilities	29,135	11,968
Measured On A Recurring Basis [Member] | 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	29,004	11,203
Measured On A Recurring Basis [Member] | 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	246,492	38,054
Measured On A Recurring Basis [Member] | 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	1,409,062	1,452,358
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | Total Fair Value [Member] | Forward Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency forward contracts	141	71
Foreign currency forward contracts	131	765
Measured On A Recurring Basis [Member] | 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	1,655,554	1,457,334
Total fair of value of liabilities	0	0
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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	246,492	38,054
Measured On A Recurring Basis [Member] | 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	1,409,062	1,419,280
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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	0	0
Foreign currency forward contracts	0
Measured On A Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total fair value of assets	141	36,490
Total fair of value of liabilities	131	765
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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	141	71
Foreign currency forward contracts	131	765
Measured On A Recurring Basis [Member] | 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	29,004	11,203
Measured On A Recurring Basis [Member] | 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	29,004	11,203
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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
Measured On A Recurring Basis [Member] | 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	0	0
Foreign currency forward contracts	$ 0	$ 0