Fair Value Of Financial Instruments (Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) (USD $) In Thousands	Sep. 30, 2011		Dec. 31, 2010
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | 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]
Investments in fixed income securities			$ 2,700
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | Measured On A Recurring Basis [Member] | Total Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities	32,136		359,160
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | 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]
Investments in fixed income securities	32,136		356,460
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | Measured On A Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities
Measured On A Recurring Basis [Member] | Money Market Funds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in money market funds	596,804		648,054
Measured On A Recurring Basis [Member] | Money Market Funds [Member] | Total Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in money market funds	596,804		648,054
Measured On A Recurring Basis [Member] | Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in money market funds
Measured On A Recurring Basis [Member] | Money Market Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in money market funds
Measured On A Recurring Basis [Member] | Corporate Debt Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities
Measured On A Recurring Basis [Member] | Corporate Debt Securities [Member] | Total Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities			141,338
Measured On A Recurring Basis [Member] | Corporate Debt Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities			141,338
Measured On A Recurring Basis [Member] | Corporate Debt Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities
Measured On A Recurring Basis [Member] | Foreign Currency Forward Contracts [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency forward contracts		[1]
Measured On A Recurring Basis [Member] | Foreign Currency Forward Contracts [Member] | Total Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency forward contracts	729	[1]
Measured On A Recurring Basis [Member] | Foreign Currency Forward Contracts [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency forward contracts	729	[1]
Measured On A Recurring Basis [Member] | Foreign Currency Forward Contracts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency forward contracts		[1]
Measured On A Recurring Basis [Member] | Debt Securities Issued By Foreign Governments [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities
Measured On A Recurring Basis [Member] | Debt Securities Issued By Foreign Governments [Member] | Total Fair Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities			5,040
Measured On A Recurring Basis [Member] | Debt Securities Issued By Foreign Governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities			5,040
Measured On A Recurring Basis [Member] | Debt Securities Issued By Foreign Governments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities
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	596,804		650,754
Contingent interest derivative on Convertible Debentures
Foreign currency forward contracts		[2]		[2]
Total fair of value of liabilities
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	629,669		1,153,592
Contingent interest derivative on Convertible Debentures	10,000		10,500
Foreign currency forward contracts	108	[2]	282	[2]
Total fair of value of liabilities	10,108		10,782
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	32,865		502,838
Contingent interest derivative on Convertible Debentures
Foreign currency forward contracts	108	[2]	282	[2]
Total fair of value of liabilities	108		282
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
Contingent interest derivative on Convertible Debentures	10,000		10,500
Foreign currency forward contracts		[2]		[2]
Total fair of value of liabilities	10,000		10,500
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments in fixed income securities			$ 2,700

[1] Included in Deferred tax assets and other current assets

[2] Included in Accounts payable and accrued liabilities