Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2015

Assets And Liabilities Measured At Fair Value On A Recurring Basis

Assets and Liabilities Measured at Fair Value on a Recurring Basis



	As of December 31, 2015		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	$	261,962	$	261,962	$	—	$	—
Money market funds	102,968		102,968		—		—
Corporate securities	3,588		—		3,588		—
Available-for-sale securities:
Agency securities	530,522		—		530,522		—
Corporate securities	697,371		—		695,809		1,562
Municipal securities	14,878		—		14,878		—
Government securities	152,045		—		152,045		—
Prepaid expenses and other current assets:
Foreign currency derivatives	1,063		—		1,063		—
Total assets	$	1,764,397	$	364,930	$	1,397,905	$	1,562
Accrued expenses and other current liabilities:
Foreign currency derivatives	3,678		—		3,678		—
Total liabilities	$	3,678	$	—	$	3,678	$	—



	As of December 31, 2014		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	$	230,370	$	230,370	$	—	$	—
Money market funds	29,512		29,512		—		—
Corporate securities	267		—		267		—
Available-for-sale securities:
Agency securities	638,313		—		638,313		—
Corporate securities	794,115		—		788,042		6,073
Municipal securities	48,730		—		48,730		—
Government securities	121,212		—		121,212		—
Prepaid expenses and other current assets:
Foreign currency derivatives	1,206		—		1,206		—
Total assets	$	1,863,725	$	259,882	$	1,597,770	$	6,073
Accrued expenses and other current liabilities:
Foreign currency derivatives	9,692		—		9,692		—
Total liabilities	$	9,692	$	—	$	9,692	$	—

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

This methodology required the Company to make assumptions that were not directly or indirectly observable regarding the fair value of the convertible debt securities; accordingly they are a Level 3 valuation and included in the table below.




	Investments
	(in thousands)
Balance at December 31, 2014	$	6,073
Purchases of Level 3 securities	1,775
Proceeds received on Level 3 securities	(501		)
Total net realized losses included in earnings	(838		)
Transfers out of Level 3	(4,947		)
Balance at December 31, 2015	$	1,562

Fair Value, by Balance Sheet Grouping

As of December 31, 2015, the fair value of the Convertible Notes, which was determined based on inputs that are observable in the market (Level 2) based on the closing trading price per $100 as of the last day of trading for the year ended December 31, 2015, and carrying value of debt instruments (carrying value excludes the equity component of the Company’s Convertible Notes classified in equity) was as follows (in thousands):



	Fair Value		Carrying Value
Convertible Senior Notes	$	1,567,364	$	1,324,992