CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock
Beginning balance at Dec. 31, 2015	$ 86,615	$ 212,115	$ 86	$ (79,948)	$ (45,638)
Beginning balance (in shares) at Dec. 31, 2015		34,845,310			6,515,894
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(39,381)			(39,381)
Unrealized gain (loss) on available-for-sale securities, net of taxes	8		8
Foreign currency translation adjustments	21		21
Repurchase of stock	$ (729)				$ (729)
Repurchase of stock (in shares)	105,750				105,750
Issuance of stock for ESPP purchase	$ 307	$ 307
Issuance of stock for ESPP purchase (in shares)		45,825
Exercise of stock options, net of shares withheld for employee taxes	2,388	$ 2,565			$ (177)
Exercise of stock options, net of shares withheld for employee taxes (in shares)		395,515			16,359
Release of restricted stock units and awards, including related stock compensation	2,257	$ 2,257
Release of restricted stock units and awards (in shares)		268,912
Stock based compensation for stock options	3,854	$ 3,854
Ending balance at Dec. 31, 2016	55,340	$ 221,098	115	(119,329)	$ (46,544)
Ending balance (in shares) at Dec. 31, 2016		35,555,562			6,638,003
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(45,291)			(45,291)
Unrealized gain (loss) on available-for-sale securities, net of taxes	(16)		(16)
Foreign currency translation adjustments	0
Repurchase of stock	$ (328)				$ (328)
Repurchase of stock (in shares)	48,687				48,687
Issuance of stock for ESPP purchase	$ 328	$ 328
Issuance of stock for ESPP purchase (in shares)		48,750
Exercise of stock options, net of shares withheld for employee taxes	518	$ 518
Exercise of stock options, net of shares withheld for employee taxes (in shares)		70,608
Release of restricted stock units and awards, including related stock compensation	2,661	$ 2,661
Release of restricted stock units and awards (in shares)		275,598
Stock based compensation for stock options	3,441	$ 3,441
Ending balance at Dec. 31, 2017	9,657	$ 228,046	99	(171,616)	$ (46,872)
Ending balance (in shares) at Dec. 31, 2017		35,950,518			6,686,690
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	54,343			54,343
Unrealized gain (loss) on available-for-sale securities, net of taxes	17		17
Foreign currency translation adjustments	$ 0
Repurchase of stock (in shares)	0
Issuance of stock for ESPP purchase	$ 218	$ 218
Issuance of stock for ESPP purchase (in shares)		26,689
Exercise of stock options, net of shares withheld for employee taxes	7,987	$ 9,465			$ (1,478)
Exercise of stock options, net of shares withheld for employee taxes (in shares)		1,452,306			136,457
Release of restricted stock units and awards, including related stock compensation	2,806	$ 2,806
Release of restricted stock units and awards (in shares)		222,985
Stock based compensation for stock options	5,880	$ 5,880
Ending balance at Dec. 31, 2018	$ 99,660	$ 246,415	$ 116	$ (98,521)	$ (48,350)
Ending balance (in shares) at Dec. 31, 2018		37,652,498			6,823,147