Changes in Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Stockholders Equity Note [Abstract]

Summary of Changes in Stockholders' Equity

The following tables summarize the changes in stockholders’ equity for the six months ended June 30, 2019 and 2018.

	Common Stock, $0.001 Par Value				Additional Paid-In		Accumulated Other Comprehensive			Accumulated
	Shares		Amount		Capital		Income (Loss)			Deficit			Total
Balances at December 31, 2018		39,300	$	40	$	589,708	$	(723	)	$	(344,384	)	$	244,641
Issuance of common stock under stock    plans, net of shares withheld for    employee taxes		440		1		1,161		—			—			1,162
Issuance of common stock in relation to    common stock offering, net of offering costs    incurred $365		2,151		2		342,628		—			—			342,630
Stock-based compensation		—		—		21,548					—			21,548
Cumulative translation adjustment		—		—		—		(304	)		—			(304	)
Unrealized gain on investments, net of income    taxes of $113		—		—		—		426			—			426
Net loss		—		—		—		—			(11,100	)		(11,100	)
Balances at March 31, 2019		41,891	$	43	$	955,045	$	(601	)	$	(355,484	)	$	599,003
Issuance of common stock under stock    plans, net of shares withheld for    employee taxes		385	$	—	$	6,595	$	—		$	—		$	6,595
Stock-based compensation		—		—		29,061		—			—			29,061
Cumulative translation adjustment		—		—		—		254			—			254
Unrealized gain on  investments, net of income    taxes of $156		—		—		—		588			—			588
Net loss		—		—		—		—			(17,357	)		(17,357	)
Balances at June 30, 2019		42,276	$	43	$	990,701	$	241		$	(372,841	)	$	618,144

	Common Stock, $0.001 Par Value				Additional Paid-In		Accumulated Other Comprehensive			Accumulated
	Shares		Amount		Capital		Income (Loss)			Deficit			Total
Balances at December 31, 2017		37,503	$	38	$	496,461	$	(57	)	$	(286,082	)	$	210,360
Issuance of common stock under stock    plans, net of shares withheld for    employee taxes		571		1		3,877		—			—			3,878
Stock-based compensation		—		—		16,596		—			—			16,596
Cumulative adjustment from adoption of    revenue recognition standard		—		—		—		—			5,793			5,793
Cumulative translation adjustment		—		—		—		298			—			298
Unrealized gain on investments, net of income    taxes of $20		—		—		—		(379	)		—			(379	)
Net loss		—		—		—		—			(15,448	)		(15,448	)
Balances at  March 31, 2018		38,074	$	39	$	516,934	$	(138	)	$	(295,737	)	$	221,098
Issuance of common stock under stock    plans, net of shares withheld for    employee taxes		459	$	—	$	5,138	$	—		$	—		$	5,138
Stock-based compensation		—		—		20,471		—			—			20,471
Cumulative adjustment from adoption of    revenue recognition standard		—		—		—		—			(267	)		(267	)
Cumulative translation adjustment		—		—		—		(720	)		—			(720	)
Unrealized gain on investments, net of income    taxes of $56		—		—		—		144			—			144
Net loss		—		—		—		—			(18,225	)		(18,225	)
Balances at June 30, 2018		38,533	$	39	$	542,543	$	(714	)	$	(314,229	)	$	227,639