Investments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring Basis

The following table summarizes the Company’s investments in marketable securities and fair value measurements by investment category reported as cash equivalents and short-term investments at December 31, 2018 (in thousands):

	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value		Level 1		Level 2
Cash equivalents:
Money market funds	$	41,027	$	—	$	—		$	41,027	$	41,027	$	—
Commercial paper	10,436		1		—			10,437		—		10,437
Municipal bonds	7,781		—		—			7,781		—		7,781
Total cash equivalents	$	59,244	$	1	$	—		$	59,245	$	41,027	$	18,218
Short-term investments:
U.S. government securities	$	22,534	$	—	$	(94	)	$	22,440	$	22,440	$	—
U.S. government agency securities	14,346		—		(56		)	14,290		—		14,290
Municipal bonds	3,548		—		(4		)	3,544		—		3,544
Foreign government securities	2,504		—		(6		)	2,498		—		2,498
Corporate debt securities	134,003		37		(685		)	133,355		—		133,355
Commercial paper	12,954		—		(4		)	12,950		—		12,950
Certificates of deposit	1,258		—		—			1,258		—		1,258
Asset-backed securities	32,054		—		(184		)	31,870		—		31,870
Total short-term investments	$	223,201	$	37	$	(1,033	)	$	222,205	$	22,440	$	199,765
Total cash equivalents and short-term investments	$	282,445	$	38	$	(1,033	)	$	281,450	$	63,467	$	217,983

The following table summarizes the Company’s investments in marketable securities and fair value measurements by investment category reported as cash equivalents and short-term investments at December 31, 2017 (in thousands):

	Carrying Amount		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value		Level 1		Level 2
Cash equivalents:
Money market funds	$	58,953	$	—	$	—		$	58,953	$	58,953	$	—
Commercial paper	21,930		—		(3		)	21,927		—		21,927
Total cash equivalents	$	80,883	$	—	$	(3	)	$	80,880	$	58,953	$	21,927
Short-term investments:
U.S. government securities	$	17,472	$	—	$	(41	)	$	17,431	$	17,431	$	—
U.S. government agency securities	11,540		—		(30		)	11,510		—		11,510
Municipal bonds	6,974		2		(8		)	6,968		—		6,968
Foreign government securities	7,499		—		(27		)	7,472		—		7,472
Corporate debt securities	105,144		3		(273		)	104,874		—		104,874
Commercial paper	30,798		1		(9		)	30,790		—		30,790
Certificates of deposit	1,255		—		—			1,255		—		1,255
Asset-backed securities	15,310		—		(76		)	15,234		—		15,234
Total short-term investments	$	195,992	$	6	$	(464	)	$	195,534	$	17,431	$	178,103
Total cash equivalents and short-term investments	$	276,875	$	6	$	(467	)	$	276,414	$	76,384	$	200,030

Unrealized Gain (Loss) on Investments

The following table summarizes the gross unrealized losses and fair values of investments in an unrealized loss position as of December 31, 2018, aggregated by investment category. No securities were in an unrealized loss position for a period of twelve months or greater.

(In thousands)	Fair Value		Gross Unrealized Loss
Short-term investments:
U.S. government securities	$	22,440	$	(94	)
U.S. government agency securities	14,290		(56		)
Municipal bonds	3,544		(4		)
Foreign government securities	2,498		(6		)
Corporate debt securities	125,192		(685		)
Commercial paper	12,950		(4		)
Asset-backed securities	31,870		(184		)
Total short-term investments in unrealized loss position	$	212,784	$	(1,033	)

The following table summarizes the gross unrealized losses and fair values of investments in an unrealized loss position as of December 31, 2017, aggregated by investment category. No securities were in an unrealized loss position for a period of twelve months or greater.

(In thousands)	Fair Value		Gross Unrealized Loss
Cash equivalents:
Commercial paper	$	19,982	$	(3	)
Total cash equivalents in unrealized loss position	$	19,982	$	(3	)
Short-term investments:
U.S. government securities	$	17,431	$	(41	)
U.S. government agency securities	11,510		(30		)
Municipal bonds	5,767		(8		)
Foreign government securities	7,472		(27		)
Corporate debt securities	103,869		(273		)
Commercial paper	27,930		(9		)
Asset-backed securities	15,234		(76		)
Total short-term investments in unrealized loss position	$	189,213	$	(464	)
Total cash equivalents and short-term investments in unrealized loss position	$	209,195	$	(467	)

Investments Classified by Contractual Maturity Date

The following table summarizes the estimated amortized cost and fair value of the Company’s marketable securities by the contractual maturity date (in thousands):

	December 31, 2018				December 31, 2017
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due less than one year	$	219,057	$	218,394	$	157,651	$	157,573
Due in one to five years	63,388		63,056		119,224		118,841
Total	$	282,445	$	281,450	$	276,875	$	276,414