Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets Measured on Recurring Basis

The following tables set 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 March 31, 2018
	Total		Level 1		Level 2		Level 3
Assets
Money market funds	$	182,149	$	182,149	$	—	$	—
U.S. government agency obligations		46,240				46,240		—
Corporate securities and commercial paper		62,386		—		62,386		—
	$	290,775	$	182,149	$	108,626	$	—

	Fair Value Measurements at December 31, 2017
	Total		Level 1		Level 2		Level 3
Assets
Money market funds	$	66,478	$	66,478	$	—	$	—
U.S. government agency obligations		57,153		—		57,153		—
Corporate securities and commercial paper		52,072		—		52,072		—
	$	175,703	$	66,478	$	109,225	$	—

Schedule of Investments Classified as Available for Sale Securities with Contractual Maturities

Classified as (with contractual maturities):

	March 31, 2018		December 31, 2017
Cash equivalents (due within 90 days)	$	198,116	$	98,426
Short-term investments (due within one year)		82,064		77,277
Long-term investments (due between one and two years)		10,595		—
	$	290,775	$	175,703

Schedule of Available for Sale Securities at Fair Value Measurements

	Fair Value Measurements at March 31, 2018
	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value
Money market funds	$	182,149	$	—	$	—		$	182,149
U.S. government agency obligations		46,283				(43	)		46,240
Corporate securities and commercial paper		62,440		—		(54	)		62,386
	$	290,872	$	—	$	(97	)	$	290,775

	Fair Value Measurements at December 31, 2017
	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value
Money market funds	$	66,478	$	—	$	—		$	66,478
U.S. government agency obligations		57,183		—		(30	)		57,153
Corporate securities and commercial paper		52,084		—		(12	)		52,072
	$	175,745	$	—	$	(42	)	$	175,703