Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Disclosures [Abstract]

Assets And Liabilities Measured At Fair Value On A Recurring Basis

Assets and Liabilities Measured at Fair Value on a Recurring Basis

	As of June 30, 2013		Quoted Prices In Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Assets:
Cash and cash equivalents:
Cash	$	204,621	$	204,621	$	—	$	—
Money market funds	47,065		47,065		—		—
Corporate securities	3,247		—		3,247		—
Agency securities	5,020		—		5,020		—
Municipal securities	3,200		—		3,200		—
Available-for-sale securities:
Agency securities	461,825		—		461,825		—
Corporate securities	629,474		—		620,383		9,091
Municipal securities	64,084		—		64,084		—
Government securities	101,204		—		101,204		—
Prepaid expenses and other current assets:
Foreign currency derivatives	4,581		—		4,581		—
Total assets	$	1,524,321	$	251,686	$	1,263,544	$	9,091
Accrued expenses and other current liabilities:
Foreign currency derivatives	7,086		—		7,086		—
Total liabilities	$	7,086	$	—	$	7,086	$	—

	As of December 31, 2012		Quoted Prices In Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Assets:
Cash and cash equivalents:
Cash	$	503,614	$	503,614	$	—	$	—
Money market funds	123,519		123,519		—		—
Corporate securities	16,476		—		16,476		—
Available-for-sale securities:
Agency securities	402,707		—		402,707		—
Corporate securities	405,322		—		401,981		3,341
Municipal securities	32,313		—		32,313		—
Government securities	39,993		—		39,993		—
Prepaid expenses and other current assets:
Foreign currency derivatives	4,157		—		4,157		—
Total assets	$	1,528,101	$	627,133	$	897,627	$	3,341
Accrued expenses and other current liabilities:
Foreign currency derivatives	4,162		—		4,162		—
Total liabilities	$	4,162	$	—	$	4,162	$	—

Assets Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs

	Investments
	(in thousands)
Balance at December 31, 2012	$	3,341
Purchases of Level 3 securities	6,000
Transfers out of Level 3	(250		)
Balance at June 30, 2013	$	9,091