CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2017	$ 591,548	$ 436	$ 628,983	$ (6,363)	$ (31,508)
Balance (in shares) at Dec. 31, 2017		43,587,079
Net income	3,448				3,448
Issuance of common stock for debt conversion
Issuance of common stock for debt conversion (in shares)		2
Exercise of stock options and releases of restricted stock	345	$ 1	344
Exercise of stock options and releases of restricted stock (in shares)		105,222
Stock-based compensation expense	2,268		2,268
Balance at Mar. 31, 2018	597,183	$ 437	631,595	(6,112)	(28,737)
Balance (in shares) at Mar. 31, 2018		43,692,303
Cumulative effect of accounting changes	(677)				(677)
Translation adjustment	251			251
Balance at Dec. 31, 2018	615,568	$ 439	642,590	(11,893)	(15,568)
Balance (in shares) at Dec. 31, 2018		43,917,378
Net income	8,053				8,053
Exercise of stock options and releases of restricted stock	44	$ 2	42
Exercise of stock options and releases of restricted stock (in shares)		156,620
Stock-based compensation expense	3,251		3,251
Balance at Mar. 31, 2019	625,025	$ 441	$ 645,883	(13,784)	$ (7,515)
Balance (in shares) at Mar. 31, 2019		44,073,998
Translation adjustment	$ (1,891)			$ (1,891)