CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2017		35,950,518			6,685,690
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)	69,883			69,883
Unrealized gain on available-for-sale securities, net of taxes	5		5
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)		922,842
Exercise of stock options, net of shares withheld for employee taxes	6,072	$ 6,072
Release of restricted stock units and awards, including related stock compensation (in shares)		156,781
Release of restricted stock units and awards, including related stock compensation	0
Stock based compensation	1,222	$ 1,222
Ending balance (in shares) at Mar. 31, 2018		37,043,975			6,685,690
Ending balance at Mar. 31, 2018	105,272	$ 235,438	104	(83,398)	$ (46,872)
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)	(11,016)			(11,016)
Unrealized gain on available-for-sale securities, net of taxes	6		6
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)		11,771
Exercise of stock options, net of shares withheld for employee taxes	71	$ 71
Release of restricted stock units and awards, including related stock compensation (in shares)		697,996
Release of restricted stock units and awards, including related stock compensation	0
Stock based compensation	2,103	$ 2,103
Ending balance (in shares) at Mar. 31, 2019		38,375,744			6,823,147
Ending balance at Mar. 31, 2019	$ 90,933	$ 248,698	$ 122	$ (109,537)	$ (48,350)