CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Earnings (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	6,185				6,185
Issuance of common stock for debt conversion	0	$ 0	0
Issuance of common stock for debt conversion (in shares)		2
Exercise of stock options and releases of restricted stock	1,490	$ 2	1,488
Exercise of stock options and releases of restricted stock (in shares)		211,491
Stock-based compensation expense	4,893		4,893
Cumulative effect of accounting changes at Dec. 31, 2017	(677)				(677)
Translation adjustment at Dec. 31, 2017	(4,780)			(4,780)
Balance at Jun. 30, 2018	598,659	$ 438	635,364	(11,143)	(26,000)
Balance (in shares) at Jun. 30, 2018		43,798,572
Balance at Mar. 31, 2018	597,183	$ 437	631,595	(6,112)	(28,737)
Balance (in shares) at Mar. 31, 2018		43,692,303
Net income	2,738				2,737
Issuance of common stock for debt conversion		$ 0	0
Exercise of stock options and releases of restricted stock	1,145	$ 1	1,144
Exercise of stock options and releases of restricted stock (in shares)		106,269
Stock-based compensation expense	2,625		2,625
Translation adjustment at Mar. 31, 2018	(5,031)			(5,031)
Balance at Jun. 30, 2018	598,659	$ 438	635,364	(11,143)	(26,000)
Balance (in shares) at Jun. 30, 2018		43,798,572
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	16,148				16,148
Issuance of common stock for debt conversion	2	$ 0	2
Issuance of common stock for debt conversion (in shares)		29
Exercise of stock options and releases of restricted stock	566	$ 3	563
Exercise of stock options and releases of restricted stock (in shares)		245,263
Issuance of common stock pursuant to the acquisition of C Technologies, Inc.	53,938	$ 8	53,930
Issuance of common stock pursuant to the acquisition of C Technologies, Inc., (in shares)		779,221
Proceeds from issuance of common stock, net of issuance costs of $0.5 million	189,623	$ 31	189,592
Proceeds from issuance of common stock, net of issuance costs of $0.5 million (in shares)		3,144,531
Stock-based compensation expense	6,283		6,283
Translation adjustment at Dec. 31, 2018	(3,160)			(3,160)
Balance at Jun. 30, 2019	878,968	$ 481	892,960	(15,053)	580
Balance (in shares) at Jun. 30, 2019		48,086,422
Balance at Mar. 31, 2019	625,025	$ 441	645,883	(13,784)	(7,515)
Balance (in shares) at Mar. 31, 2019		44,073,998
Net income	8,095				8,095
Issuance of common stock for debt conversion	2	$ 0	2
Issuance of common stock for debt conversion (in shares)		29
Exercise of stock options and releases of restricted stock	523	$ 1	522
Exercise of stock options and releases of restricted stock (in shares)		88,643
Issuance of common stock pursuant to the acquisition of C Technologies, Inc.	53,938	$ 8	53,930
Issuance of common stock pursuant to the acquisition of C Technologies, Inc., (in shares)		779,221
Proceeds from issuance of common stock, net of issuance costs of $0.5 million	189,623	$ 31	189,592
Proceeds from issuance of common stock, net of issuance costs of $0.5 million (in shares)		3,144,531
Stock-based compensation expense	3,031		3,031
Translation adjustment at Mar. 31, 2019	(1,269)			(1,269)
Balance at Jun. 30, 2019	$ 878,968	$ 481	$ 892,960	$ (15,053)	$ 580
Balance (in shares) at Jun. 30, 2019		48,086,422