Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017						26,828,651
Balance at Dec. 31, 2017						$ 27	$ 241,725	$ 224,697	$ (5,234)	$ 461,215
Common shares issued on exercise of options and other (in shares)						260,694
Common shares issued on exercise of options and other						$ 0	6,791	0	0	6,791
Stock-based compensation expense						$ 0	10,928	0	0	10,928
Repurchases of Common Stock (in shares)						(104,598)
Repurchases of Common Stock						$ 0	(942)	(11,287)	0	(12,229)
Net income						0	0	76,588	0	76,588
Foreign currency translation adjustments						$ 0	0	0	(3,258)	(3,258)
Comprehensive income										73,330
Balance (in shares) at Dec. 31, 2018						26,984,747
Balance (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2018	$ 0	$ 0	$ 1,462	$ 0	$ 1,462
Balance at Dec. 31, 2018						$ 27	258,502	291,460	(8,492)	541,497
Common shares issued on exercise of options and other (in shares)						128,174
Common shares issued on exercise of options and other						$ 0	1,904	0	0	1,904
Stock-based compensation expense						$ 0	10,781	0	0	10,781
Repurchases of Common Stock (in shares)						(326,462)
Repurchases of Common Stock						$ 0	(3,128)	(30,393)	0	(33,521)
Net income								63,655		63,655
Foreign currency translation adjustments						$ 0	0	0	1,474	1,474
Comprehensive income										$ 65,129
Balance (in shares) at Dec. 31, 2019						26,786,459				26,786,459
Balance at Dec. 31, 2019						$ 27	268,059	324,722	(7,018)	$ 585,790
Common shares issued on exercise of options and other (in shares)						189,951
Common shares issued on exercise of options and other						$ 0	4,114	0	0	4,114
Stock-based compensation expense						$ 0	14,673	0	0	14,673
Repurchases of Common Stock (in shares)						(199,614)
Repurchases of Common Stock						$ 0	(1,998)	(12,688)	0	(14,686)
Net income						0	0	50,867	0	50,867
Foreign currency translation adjustments						$ 0	0	0	3,598	3,598
Comprehensive income										$ 54,465
Balance (in shares) at Dec. 31, 2020						26,776,796				26,776,796
Balance at Dec. 31, 2020						$ 27	$ 284,848	$ 362,901	$ (3,420)	$ 644,356