Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2014

Fair Value Disclosures [Abstract]

Summary of the valuation of cash equivalents and marketable securities by pricing levels

The following table presents the financial instruments that are carried at fair value and summarizes the valuation of its cash equivalents and marketable securities by the above pricing levels as of June 30, 2014 and December 31, 2013:

	As of June 30, 2014
	Total		Quoted Market Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
Money market funds	$	79,522	$	79,522	$	—	$	—
Corporate notes, bonds and commercial paper	146,859		—		146,859		—
Total available-for-sale securities	$	226,381	$	79,522	$	146,859	$	—

	As of December 31, 2013
	Total		Quoted Market Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
Money market funds	$	300,605	$	300,605	$	—	$	—
Corporate notes, bonds and commercial paper	58,492		—		58,492		—
Total available-for-sale securities	$	359,097	$	300,605	$	58,492	$	—

Financial instruments that are measured and carried at cost on a nonrecurring basis

The following table presents the financial instruments that are measured on a nonrecurring basis as of June 30, 2014:

	As of June 30, 2014
(in thousands)	Carrying Value		Quoted market prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)		Impairment charges for the six months ended June 30, 2014
Investment in non-marketable security	$	600	$	—	$	—	$	600	$	—

Financial instruments not carried at fair value but requiring fair value disclosure

The following table presents the financial instruments that are not carried at fair value but require fair value disclosure as of June 30, 2014 and December 31, 2013:

	As of June 30, 2014						As of December 31, 2013
(In thousands)	Face Value		Carrying Value		Fair Value		Face Value		Carrying Value		Fair Value
5% Convertible Senior Notes due 2014 (the "2014 Notes")	$	—	$	—	$	—	$	172,500	$	164,047	$	175,821
1.125% Convertible Senior Notes due 2018 (the "2018 Notes")	$	138,000	$	112,316	$	185,189	$	138,000	$	109,629	$	142,427