Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2014

Fair Value Disclosures [Abstract]

Financial assets subject to fair value measurements (excluding restricted cash and cash equivalents (Alios))

The following table sets forth the Company’s financial assets subject to fair value measurements:

	Fair Value Measurements as of June 30, 2014
			Fair Value Hierarchy
	Total		Level 1		Level 2		Level 3
	(in thousands)
Financial assets carried at fair value:
Cash equivalents:
Money market funds	$	123,469	$	123,469	$	—	$	—
Marketable securities:
Government-sponsored enterprise securities	497,587		497,587		—		—
Commercial paper	69,243		—		69,243		—
Corporate debt securities	231,773		—		231,773		—
Total	$	922,072	$	621,056	$	301,016	$	—