Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance (in shares) at Dec. 31, 2018	32,558
Balance at Dec. 31, 2018	$ 33	$ 565,116	$ (157,260)	$ 448	$ 408,337
Increase (Decrease) in Stockholders' Equity
Net income			6,062		6,062
Foreign currency translation adjustments				(495)	(495)
Change in pension obligation				30	30
Exercise of stock options (in shares)	288
Exercise of stock options		1,828			1,828
Issuance of restricted common shares (in shares)	35
Issuance of restricted common shares		(281)			(281)
Stock-based compensation expense		1,672			1,672
Balance (in shares) at Mar. 31, 2019	32,881
Balance at Mar. 31, 2019	$ 33	568,335	(151,198)	(17)	417,153
Balance (in shares) at Dec. 31, 2019	32,585
Balance at Dec. 31, 2019	$ 33	559,878	(140,226)	(258)	419,427
Increase (Decrease) in Stockholders' Equity
Net income			11,221		11,221
Foreign currency translation adjustments				(1,112)	(1,112)
Change in pension obligation				57	57
Exercise of stock options (in shares)	540
Exercise of stock options	$ 1	4,498			4,499
Issuance of shares under Employee Stock Purchase Plan (in shares)	1
Issuance of shares under Employee Stock Purchase Plan		19			19
Issuance of restricted common shares (in shares)	69
Issuance of restricted common shares		(1,162)			(1,162)
Stock-based compensation expense		1,724			1,724
Repurchase of common stock (in shares)	(358)
Repurchase of common stock	$ (1)	(5,775)	(1,725)		(7,501)
Balance (in shares) at Mar. 31, 2020	32,837
Balance at Mar. 31, 2020	$ 33	$ 559,182	$ (130,730)	$ (1,313)	$ 427,172