Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Summary of Fair Value Assets and Liabilities Measured on Recurring Basis

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):

	Fair Value Measurements at September 30, 2017
	Total		Level 1		Level 2		Level 3
Assets
Money market funds	$	227,466	$	227,466	$	—	$	—
U.S. government agency obligations		31,963		—		31,963		—
Corporate securities		24,033		—		24,033		—
Total	$	283,462	$	227,466	$	55,996	$	—
	Fair Value Measurements at December 31, 2016
	Total		Level 1		Level 2		Level 3
Assets
Money market funds	$	136,481	$	136,481	$	—	$	—
U.S. government agency obligations		12,075		—		12,075		—
Corporate securities		3,999		—		3,999		—
Total	$	152,555	$	136,481	$	16,074	$	—

Summary of Fair Value Measurement of Available-for-sale Securities

The following table is a summary of amortized cost, unrealized gain and loss, and fair value (in thousands) of the Company’s marketable securities by contractual maturities:

	Fair Value Measurements at September 30, 2017
	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash equivalents (due within 90 days)	$	227,466	$	—	$	—		$	227,466
Short-term investments (due within one year)		20,009		—		(16	)	$	19,993
Long-term investments (due between one and two years)		36,033		3		(33	)	$	36,003
Total	$	283,508	$	3	$	(49	)	$	283,462
	FairValue Measurements at December 31, 2016
	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value
Cash equivalents (due within 90 days)	$	136,481	$	—	$	—		$	136,481
Short-term investments (due within one year)		4,072		—		—			4,072
Long-term investments (due between one and two years)		11,988		14		—			12,002
Total	$	152,541	$	14	$	—		$	152,555