Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	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, net of shares withheld for tax obligations (in shares)	102,895
Common shares issued on exercise of options and other, net of shares withheld for tax obligations		2,250			2,250
Stock-based compensation expense		2,307			2,307
Repurchases of common stock (in shares)
Repurchases of common stock
Net income			18,051		18,051
Foreign currency translation adjustment				2,393	2,393
Comprehensive income					20,444
Balance (in shares) at Mar. 31, 2018	26,931,546
Balance at Mar. 31, 2018	$ 27	246,282	244,208	(2,841)	487,676
Other comprehensive income
Foreign currency translation adjustment				2,393	2,393
Comprehensive income					20,444
Balance (in shares) at Mar. 31, 2018	26,931,546
Balance at Mar. 31, 2018	$ 27	246,282	244,208	(2,841)	487,676
Revenue recognition transition adjustment			1,460		$ 1,460
Balance (in shares) at Dec. 31, 2018	26,984,747				26,984,747
Balance at Dec. 31, 2018	$ 27	258,502	291,460	(8,492)	$ 541,497
Common shares issued on exercise of options and other, net of shares withheld for tax obligations (in shares)	19,950
Common shares issued on exercise of options and other, net of shares withheld for tax obligations		(420)			(420)
Stock-based compensation expense		3,040			3,040
Repurchases of common stock (in shares)	(157,716)
Repurchases of common stock		(1,511)	(15,798)		(17,309)
Net income			15,511		15,511
Foreign currency translation adjustment				476	476
Comprehensive income					$ 15,987
Balance (in shares) at Mar. 31, 2019	26,846,981				26,846,981
Balance at Mar. 31, 2019	$ 27	259,611	291,173	(8,016)	$ 542,795
Other comprehensive income
Foreign currency translation adjustment				476	476
Comprehensive income					$ 15,987
Balance (in shares) at Mar. 31, 2019	26,846,981				26,846,981
Balance at Mar. 31, 2019	$ 27	$ 259,611	$ 291,173	$ (8,016)	$ 542,795