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, net of shares withheld (in shares)	35
Issuance of restricted common shares, net of shares withheld		(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, 2018	32,558
Balance at Dec. 31, 2018	$ 33	565,116	(157,260)	448	408,337
Increase (Decrease) in Stockholders' Equity
Net income					6,618
Foreign currency translation adjustments					(714)
Change in pension obligation					59
Balance (in shares) at Jun. 30, 2019	32,297
Balance at Jun. 30, 2019	$ 32	556,283	(150,642)	(207)	405,466
Balance (in shares) at Mar. 31, 2019	32,881
Balance at Mar. 31, 2019	$ 33	568,335	(151,198)	(17)	417,153
Increase (Decrease) in Stockholders' Equity
Net income			556		556
Foreign currency translation adjustments				(219)	(219)
Change in pension obligation				29	29
Exercise of stock options (in shares)	104
Exercise of stock options		567			567
Issuance of shares under Employee Stock Purchase Plan (in shares)	32
Issuance of shares under Employee Stock Purchase Plan		479			479
Issuance of restricted common shares, net of shares withheld (in shares)	165
Issuance of restricted common shares, net of shares withheld		(1,310)			(1,310)
Stock-based compensation expense		2,246			2,246
Repurchase of common stock (in shares)	(885)
Repurchase of common stock	$ (1)	(14,034)			(14,035)
Balance (in shares) at Jun. 30, 2019	32,297
Balance at Jun. 30, 2019	$ 32	556,283	(150,642)	(207)	405,466
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, net of shares withheld (in shares)	69
Issuance of restricted common shares, net of shares withheld		(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
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					24,523
Foreign currency translation adjustments					(276)
Change in pension obligation					114
Balance (in shares) at Jun. 30, 2020	33,433
Balance at Jun. 30, 2020	$ 33	562,839	(117,428)	(420)	445,024
Balance (in shares) at Mar. 31, 2020	32,837
Balance at Mar. 31, 2020	$ 33	559,182	(130,730)	(1,313)	427,172
Increase (Decrease) in Stockholders' Equity
Net income			13,302		13,302
Foreign currency translation adjustments				836	836
Change in pension obligation				57	57
Exercise of stock options (in shares)	343
Exercise of stock options		2,783			2,783
Issuance of shares under Employee Stock Purchase Plan (in shares)	21
Issuance of shares under Employee Stock Purchase Plan		490			490
Issuance of restricted common shares, net of shares withheld (in shares)	232
Issuance of restricted common shares, net of shares withheld		(2,698)			(2,698)
Stock-based compensation expense		3,082			3,082
Balance (in shares) at Jun. 30, 2020	33,433
Balance at Jun. 30, 2020	$ 33	$ 562,839	$ (117,428)	$ (420)	$ 445,024