CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings (Accumulated deficit)
Beginning balance (in shares) at Dec. 31, 2017		32,878,000
Beginning balance at Dec. 31, 2017	$ 22,032	$ 33	$ 50,495	$ (28,496)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Options exercised (in shares)		28,000
Options exercised	65		65
Stock based compensation	1,238		1,238
Shares issued on net settlement of warrants (in shares)		17,000
Shares issued on net settlement of warrants	$ 0
Shares issued on net settlement of stock options (in shares)	713,980	697,000
Shares issued on net settlement of stock options	$ 0
Net income (loss)	67,967			67,967
Ending balance (in shares) at Sep. 30, 2018		33,620,000
Ending balance at Sep. 30, 2018	91,302	$ 33	51,798	39,471
Beginning balance (in shares) at Jun. 30, 2018		32,913,000
Beginning balance at Jun. 30, 2018	21,574	$ 33	51,244	(29,703)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Options exercised (in shares)		28,000
Options exercised	65		65
Stock based compensation	$ 489		489
Shares issued on net settlement of stock options (in shares)	680,388	679,000
Shares issued on net settlement of stock options	$ 0
Net income (loss)	69,174			69,174
Ending balance (in shares) at Sep. 30, 2018		33,620,000
Ending balance at Sep. 30, 2018	91,302	$ 33	51,798	39,471
Beginning balance (in shares) at Dec. 31, 2018		33,705,000
Beginning balance at Dec. 31, 2018	87,885	$ 34	52,920	34,931
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Options exercised (in shares)		51,000
Options exercised	154		154
Stock based compensation	$ 2,594		2,594
Shares issued on net settlement of stock options (in shares)	220,879	221,000
Shares issued on net settlement of stock options	$ 0
Net income (loss)	(13,900)			(13,900)
Ending balance (in shares) at Sep. 30, 2019		33,977,000
Ending balance at Sep. 30, 2019	76,733	$ 34	55,668	21,031
Beginning balance (in shares) at Jun. 30, 2019		33,921,000
Beginning balance at Jun. 30, 2019	80,462	$ 34	55,086	25,342
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Options exercised (in shares)		21,000
Options exercised	39		39
Stock based compensation	$ 543		543
Shares issued on net settlement of stock options (in shares)	34,928	35,000
Shares issued on net settlement of stock options	$ 0
Net income (loss)	(4,311)			(4,311)
Ending balance (in shares) at Sep. 30, 2019		33,977,000
Ending balance at Sep. 30, 2019	$ 76,733	$ 34	$ 55,668	$ 21,031