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	$ 0	2,250	0	0	2,250
Stock-based compensation expense	0	2,307	0	0	2,307
Repurchases of common stock	0	0	0	0	0
Net income	0	0	18,051	0	18,051
Foreign currency translation adjustment	$ 0	0	0	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
Balance (in shares) at Dec. 31, 2017	26,828,651
Balance at Dec. 31, 2017	$ 27	241,725	224,697	(5,234)	461,215
Net income					36,365
Comprehensive income					35,240
Balance (in shares) at Jun. 30, 2018	27,026,394
Balance at Jun. 30, 2018	$ 27	250,063	262,522	(6,359)	506,253
Revenue recognition transition adjustment	$ 0	0	1,460	0	1,460
Balance (in shares) at Mar. 31, 2018	26,931,546
Balance at Mar. 31, 2018	$ 27	246,282	244,208	(2,841)	487,676
Common shares issued on exercise of options and other, net of shares withheld for tax obligations (in shares)	94,848
Common shares issued on exercise of options and other, net of shares withheld for tax obligations	$ 0	1,054	0	0	1,054
Stock-based compensation expense	0	2,727	0	0	2,727
Repurchases of common stock	0	0	0	0	0
Net income	0	0	18,314	0	18,314
Foreign currency translation adjustment	$ 0	0	0	(3,518)	(3,518)
Comprehensive income					14,796
Balance (in shares) at Jun. 30, 2018	27,026,394
Balance at Jun. 30, 2018	$ 27	250,063	262,522	(6,359)	$ 506,253
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	$ 0	(420)	0	0	(420)
Stock-based compensation expense	$ 0	3,040	0	0	3,040
Repurchases of common stock (in shares)	(157,716)
Repurchases of common stock	$ 0	(1,511)	(15,798)	0	(17,309)
Net income	0	0	15,511	0	15,511
Foreign currency translation adjustment	$ 0	0	0	476	476
Comprehensive income					15,987
Balance (in shares) at Mar. 31, 2019	26,846,981
Balance at Mar. 31, 2019	$ 27	259,611	291,173	(8,016)	$ 542,795
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
Net income					31,677
Comprehensive income					$ 31,675
Balance (in shares) at Jun. 30, 2019	26,882,097				26,882,097
Balance at Jun. 30, 2019	$ 27	262,952	303,628	(8,494)	$ 558,113
Balance (in shares) at Mar. 31, 2019	26,846,981
Balance at Mar. 31, 2019	$ 27	259,611	291,173	(8,016)	542,795
Common shares issued on exercise of options and other, net of shares withheld for tax obligations (in shares)	75,785
Common shares issued on exercise of options and other, net of shares withheld for tax obligations	$ 0	245	0	0	245
Stock-based compensation expense	$ 0	3,486	0	0	3,486
Repurchases of common stock (in shares)	(40,669)
Repurchases of common stock	$ 0	(390)	(3,711)	0	(4,101)
Net income	0	0	16,166	0	16,166
Foreign currency translation adjustment	$ 0	0	0	(478)	(478)
Comprehensive income					$ 15,688
Balance (in shares) at Jun. 30, 2019	26,882,097				26,882,097
Balance at Jun. 30, 2019	$ 27	$ 262,952	$ 303,628	$ (8,494)	$ 558,113