CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2017		35,950,518			6,686,690
Beginning balance at Dec. 31, 2017	$ 9,657	$ 228,046	$ 99	$ (171,616)	$ (46,872)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	62,125			62,125
Unrealized gain on available-for-sale securities, net of taxes	10		10
Issuance of stock for ESPP purchase (in shares)		13,834
Issuance of stock for ESPP purchase	98	$ 98
Exercise of stock options, net of shares withheld for employee taxes (in shares)		1,322,031			39,695
Exercise of stock options, net of shares withheld for employee taxes	7,980	$ 8,549			$ (569)
Release of restricted stock units and awards (in shares)		202,152
Release of restricted stock units and awards	0
Stock based compensation	3,752	$ 3,752
Ending balance (in shares) at Jun. 30, 2018		37,488,535			6,726,385
Ending balance at Jun. 30, 2018	101,957	$ 240,445	109	(91,156)	$ (47,441)
Beginning balance (in shares) at Mar. 31, 2018		37,043,975			6,685,690
Beginning balance at Mar. 31, 2018	105,272	$ 235,438	104	(83,398)	$ (46,872)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(7,758)			(7,758)
Unrealized gain on available-for-sale securities, net of taxes	5		5
Exercise of stock options, net of shares withheld for employee taxes (in shares)		399,189			40,695
Exercise of stock options, net of shares withheld for employee taxes	1,908	$ 2,477			$ (569)
Release of restricted stock units and awards (in shares)		45,371
Release of restricted stock units and awards	0
Stock based compensation	2,530	$ 2,530
Ending balance (in shares) at Jun. 30, 2018		37,488,535			6,726,385
Ending balance at Jun. 30, 2018	101,957	$ 240,445	109	(91,156)	$ (47,441)
Beginning balance (in shares) at Dec. 31, 2018		37,652,498			6,823,147
Beginning balance at Dec. 31, 2018	99,660	$ 246,415	116	(98,521)	$ (48,350)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(19,636)			(19,636)
Unrealized gain on available-for-sale securities, net of taxes	22		22
Issuance of stock for ESPP purchase (in shares)		13,479
Issuance of stock for ESPP purchase	109	$ 109
Exercise of stock options, net of shares withheld for employee taxes (in shares)		61,798
Exercise of stock options, net of shares withheld for employee taxes	371	$ 371
Release of restricted stock units and awards (in shares)		760,552
Release of restricted stock units and awards	0
Stock based compensation	3,184	$ 3,184
Ending balance (in shares) at Jun. 30, 2019		38,488,327			6,823,147
Ending balance at Jun. 30, 2019	83,710	$ 250,079	138	(118,157)	$ (48,350)
Beginning balance (in shares) at Mar. 31, 2019		38,375,744			6,823,147
Beginning balance at Mar. 31, 2019	90,933	$ 248,698	122	(109,537)	$ (48,350)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(8,620)			(8,620)
Unrealized gain on available-for-sale securities, net of taxes	16		16
Exercise of stock options, net of shares withheld for employee taxes (in shares)		50,027
Exercise of stock options, net of shares withheld for employee taxes	300	$ 300
Release of restricted stock units and awards (in shares)		62,556
Release of restricted stock units and awards	0
Stock based compensation	1,081	$ 1,081
Ending balance (in shares) at Jun. 30, 2019		38,488,327			6,823,147
Ending balance at Jun. 30, 2019	$ 83,710	$ 250,079	$ 138	$ (118,157)	$ (48,350)