CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit
Balance, beginning of period (in shares) at Dec. 31, 2015		109,467,416		2,105,945
Balance, beginning of period at Dec. 31, 2015	$ 34,724	$ 109	$ 163,438	$ (17,125)	$ (111,698)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	17,732		17,732
Tax benefit of share-based compensation	(423)		(423)
Exercise of stock options (in shares)		243,928		(918,544)
Exercise of stock options	3,494	$ 0	(3,767)	$ 7,261
Issuance of restricted stock (in shares)		501,203		(2,210,879)
Issuance of restricted stock	0	$ 1	(17,546)	$ 17,545
Restricted stock shares canceled/forfeited (in shares)				377,317
Restricted stock cancellation / forfeited	$ 0		2,503	$ (2,503)
Shares issued for services performed (in shares)	(43,344)			(43,344)
Shares issued for services performed	$ 346		6	$ 340
Shares issued in conjunction with acquisition of Stability (in shares)	(441,009)			(441,009)
Shares issued in conjunction with acquisition of Stability	$ 3,347		(462)	$ 3,809
Share repurchase (in shares)	(1,338,616)			1,338,616
Shares repurchased	$ (10,378)			$ (10,378)
Shares repurchased for tax withholding on vesting of restricted stock units (in shares)				141,658
Shares repurchased for tax withholding on vesting of restricted stock units	(1,165)			$ (1,165)
Net income (loss)	390				390
Balance, end of period (in shares) at Dec. 31, 2016		110,212,547		349,760
Balance, end of period at Dec. 31, 2016	48,067	$ 110	161,481	$ (2,216)	(111,308)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	21,195		21,195
Exercise of stock options (in shares)		1,097,933		(1,396,803)
Exercise of stock options	11,987	$ 1	(3,433)	$ 15,419
Issuance of restricted stock (in shares)		1,393,446		(1,954,068)
Issuance of restricted stock	0	$ 2	(17,840)	$ 17,838
Restricted stock shares canceled/forfeited (in shares)				320,117
Restricted stock cancellation / forfeited	$ 0		3,205	$ (3,205)
Shares issued for services performed (in shares)	(17,539)			(17,539)
Shares issued for services performed	$ 166		41	$ 125
Shares issued in conjunction with acquisition of Stability	$ 0
Share repurchase (in shares)	(5,635,077)			5,635,077
Shares repurchased	$ (68,263)			$ (68,263)
Shares repurchased for tax withholding on vesting of restricted stock units (in shares)				419,865
Shares repurchased for tax withholding on vesting of restricted stock units	(4,082)			$ (4,082)
Net income (loss)	64,727				64,727
Balance, end of period (in shares) at Dec. 31, 2017		112,703,926		3,356,409
Balance, end of period at Dec. 31, 2017	73,797	$ 113	164,649	$ (44,384)	(46,581)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	$ 14,768		14,768
Exercise of stock options (in shares)	786,708			(786,708)
Exercise of stock options	$ 3,555		(8,210)	$ 11,765
Issuance of restricted stock (in shares)				(1,947,475)
Issuance of restricted stock	0		(25,657)	$ 25,657
Restricted stock shares canceled/forfeited (in shares)				1,861,314
Restricted stock cancellation / forfeited	0		19,194	$ (19,194)
Shares issued for services performed	0
Shares issued in conjunction with acquisition of Stability	$ 0
Share repurchase (in shares)	(507,600)			507,600
Shares repurchased	$ (7,572)			$ (7,572)
Shares repurchased for tax withholding on vesting of restricted stock units (in shares)				614,123
Shares repurchased for tax withholding on vesting of restricted stock units	(4,914)			$ (4,914)
Net income (loss)	(29,979)
Balance, end of period (in shares) at Dec. 31, 2018		112,703,926		3,605,263
Balance, end of period at Dec. 31, 2018	$ 49,655	$ 113	$ 164,744	$ (38,642)	$ (76,560)