Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Schedule of Cash and Cash Equivalents, Available-for-sale Securities Reconciliation

The Company's cash and cash equivalents, short-term investments, and long-term investments consist of the following:

	June 30, 2015
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Cash and cash equivalents:
Cash	$	41,300	$	—	$	—		$	41,300
Money market funds	21,061		—		—			21,061
Commercial paper	21,694		3		—			21,697
Total	84,055		3		—			84,058
Short-term investments:
Commercial paper	15,929		7		—			15,936
Corporate bonds	12,688		1		(6		)	12,683
Asset-backed securities	71		—		—			71
U.S. government agencies	45,342		20		—			45,362
Total	74,030		28		(6		)	74,052
Long-term investments:
Asset-backed securities	9,999		1		—			10,000
U.S. government agencies	11,940		9		(4		)	11,945
Corporate bonds	7,090		1		(5		)	7,086
Total	29,029		11		(9		)	29,031
Total	$	187,114	$	42	$	(15	)	$	187,141

	December 31, 2014
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Cash and cash equivalents:
Cash	$	36,024	$	—	$	—		$	36,024
Money market funds	39,180		—		—			39,180
U.S. government agencies	300		—		—			300
Commercial paper	1,000		—		—			1,000
Total	76,504		—		—			76,504
Short-term investments:
Commercial paper	4,998		1		—			4,999
Corporate bonds	12,438		6		(6		)	12,438
U.S. government agencies	33,280		3		(6		)	33,277
Total	50,716		10		(12		)	50,714
Long-term investments:
Asset-backed securities	16,092		5		(3		)	16,094
U.S. government agencies	20,243		22		(10		)	20,255
Corporate bonds	3,101		—		(2		)	3,099
Total	39,436		27		(15		)	39,448
Total	$	166,656	$	37	$	(27	)	$	166,666

Schedule of Assets Measured on Recurring Basis

The following table sets forth by level within the fair value hierarchy the fair value of the Company's available-for-sale securities measured on a recurring basis, excluding cash and money market funds:

	June 30, 2015
	Level 1		Level 2		Level 3		Fair Value
	(in thousands)
Commercial paper	$	—	$	37,633	$	—	$	37,633
U.S. government agencies	—		57,307		—		57,307
Corporate bonds	—		19,769		—		19,769
Asset-backed securities	—		10,071		—		10,071
Total	$	—	$	124,780	$	—	$	124,780

	December 31, 2014
	Level 1		Level 2		Level 3		Fair Value
	(in thousands)
Commercial paper	$	—	$	5,999	$	—	$	5,999
U.S. government agencies	—		53,832		—		53,832
Corporate bonds	—		15,537		—		15,537
Asset-backed securities	—		16,094		—		16,094
Total	$	—	$	91,462	$	—	$	91,462

Schedule of Available-for-Sale Securities by Contractual Maturity

The following summarizes the fair value of securities classified as available-for-sale by contractual maturity:

	June 30, 2015
	Mature within One Year		After One Year through Two Years		Over Two Years		Fair Value
	(in thousands)
Commercial paper	$	37,633	$	—	$	—	$	37,633
U.S. government agencies	45,362		11,945		—		57,307
Corporate bonds	12,683		7,086		—		19,769
Asset-backed securities	72		7,502		2,497		10,071
Total	$	95,750	$	26,533	$	2,497	$	124,780

	December 31, 2014
	Mature within One Year		After One Year through Two Years		Over Two Years		Fair Value
	(in thousands)
Commercial paper	$	5,999	$	—	$	—	$	5,999
U.S. government agencies	33,577		20,255		—		53,832
Corporate bonds	12,438		3,099		—		15,537
Asset-backed securities	—		7,327		8,767		16,094
Total	$	52,014	$	30,681	$	8,767	$	91,462