Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Total assets	$ 1,661,208	$ 1,528,101
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	2,822	4,162
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Total assets	240,224	627,133
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Total assets	1,411,893	897,627
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	2,822	4,162
Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Total assets	9,091	3,341
Liabilities, Fair Value Disclosure [Abstract]
Total liabilities	0	0
Prepaid Expenses and Other Current Assets [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Foreign currency derivatives	5,117	4,157
Prepaid Expenses and Other Current Assets [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Foreign currency derivatives	0	0
Prepaid Expenses and Other Current Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Foreign currency derivatives	5,117	4,157
Prepaid Expenses and Other Current Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Foreign currency derivatives	0	0
Accrued Expenses And Other Current Liabilities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	2,822	4,162
Accrued Expenses And Other Current Liabilities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	0	0
Accrued Expenses And Other Current Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	2,822	4,162
Accrued Expenses And Other Current Liabilities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Liabilities, Fair Value Disclosure [Abstract]
Foreign currency derivatives	0	0
Cash [Member] | Cash and Cash Equivalents [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	189,065	503,614
Cash [Member] | Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	189,065	503,614
Cash [Member] | Cash and Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Cash [Member] | Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Money Market Funds [Member] | Cash and Cash Equivalents [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	51,159	123,519
Money Market Funds [Member] | Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	51,159	123,519
Money Market Funds [Member] | Cash and Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Money Market Funds [Member] | Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Corporate Debt Securities [Member] | Cash and Cash Equivalents [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	4,249	16,476
Corporate Debt Securities [Member] | Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Corporate Debt Securities [Member] | Cash and Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	4,249	16,476
Corporate Debt Securities [Member] | Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0	0
Corporate Debt Securities [Member] | Available-For-Sale Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	679,723	405,322
Corporate Debt Securities [Member] | Available-For-Sale Securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Corporate Debt Securities [Member] | Available-For-Sale Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	670,632	401,981
Corporate Debt Securities [Member] | Available-For-Sale Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	9,091	3,341
Government Securities [Member] | Available-For-Sale Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	128,508	39,993
Government Securities [Member] | Available-For-Sale Securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Government Securities [Member] | Available-For-Sale Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	128,508	39,993
Government Securities [Member] | Available-For-Sale Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Municipal Securities [Member] | Cash and Cash Equivalents [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	2,000
Municipal Securities [Member] | Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0
Municipal Securities [Member] | Cash and Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	2,000
Municipal Securities [Member] | Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and cash equivalents	0
Municipal Securities [Member] | Available-For-Sale Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	72,959	32,313
Municipal Securities [Member] | Available-For-Sale Securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Municipal Securities [Member] | Available-For-Sale Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	72,959	32,313
Municipal Securities [Member] | Available-For-Sale Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Agency Securities [Member] | Available-For-Sale Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	528,428	402,707
Agency Securities [Member] | Available-For-Sale Securities [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	0	0
Agency Securities [Member] | Available-For-Sale Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	528,428	402,707
Agency Securities [Member] | Available-For-Sale Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities	$ 0	$ 0