CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit	Total
BALANCE at Dec. 31, 2018	$ 11	$ 462,004	$ (3,831)	$ (404,067)	$ 54,117
BALANCE (in shares) at Dec. 31, 2018	106,206,545
Issuance of common stock for stock option exercises		798			798
Issuance of common stock for stock option exercises (in shares)	250,468
Issuance of common stock pursuant to the Employee Stock Purchase Plan		2,047			2,047
Issuance of common stock pursuant to the Employee Stock Purchase Plan (in shares)	518,112
Issuance of common stock pursuant to the Employee Stock-Settled Bonus Plans		10,485			10,485
Issuance of common stock pursuant to the Employee Stock-Settled Bonus Plans (in shares)	2,170,855
Shares withheld for net settlement of equity awards		(4,409)			(4,409)
Shares withheld for net settlement of equity awards (in shares)	(894,194)
Repurchase of common stock			(3,601)		(3,601)
Repurchase of common stock (in shares)	(738,966)
Vesting of restricted stock units (in shares)	1,157,600
Stock-based compensation		6,464			6,464
Net loss				(17,100)	(17,100)
BALANCE at Mar. 31, 2019	$ 11	477,389	(7,432)	(421,167)	48,801
BALANCE (in shares) at Mar. 31, 2019	108,670,420
BALANCE at Dec. 31, 2019	$ 11	504,041	(15,141)	(452,913)	35,998
BALANCE (in shares) at Dec. 31, 2019	112,725,391
Issuance of common stock for stock option exercises		117			$ 117
Issuance of common stock for stock option exercises (in shares)	29,797				29,797
Issuance of common stock pursuant to the Employee Stock Purchase Plan		2,151			$ 2,151
Issuance of common stock pursuant to the Employee Stock Purchase Plan (in shares)	562,233
Issuance of common stock pursuant to the Employee Stock-Settled Bonus Plans	$ 1	7,633			7,634
Issuance of common stock pursuant to the Employee Stock-Settled Bonus Plans (in shares)	1,730,682
Shares withheld for net settlement of equity awards		(3,182)			$ (3,182)
Shares withheld for net settlement of equity awards (in shares)	(738,233)				(738,233)
Repurchase of common stock			(684)		$ (684)
Repurchase of common stock (in shares)	(210,618)				(210,618)
Vesting of restricted stock units (in shares)	1,270,507
Stock-based compensation		6,815			$ 6,815
Net loss				(12,661)	(12,661)
BALANCE at Mar. 31, 2020	$ 12	$ 517,575	$ (15,825)	$ (465,574)	$ 36,188
BALANCE (in shares) at Mar. 31, 2020	115,369,759