Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2015	$ 523,276	$ 21	$ 280,113	$ 325,306	$ (74,673)	$ (7,491)
Balance (in shares) at Dec. 31, 2015		19,032			2,282
Net income	46,584			46,584
Other comprehensive income (loss)	(2,149)					(2,149)
Equity compensation	9,082		8,734		$ 348
Exercise of stock options	3,034	$ 1	3,033
Exercise of stock options (in shares)		128
Issuance of shares pursuant to vesting of restricted stock units		221
Net payments for stock issuances and buybacks	(13,823)		547		$ (14,370)
Net payments for stock issuances and buybacks (in shares)		(360)			360
Balance at Dec. 31, 2016	566,004	$ 22	292,427	371,890	$ (88,695)	(9,640)
Balance (in shares) at Dec. 31, 2016		19,021			2,642
Net income	62,876			62,876
Other comprehensive income (loss)	4,601					4,601
Equity compensation	10,291		9,985		$ 306
Exercise of stock options	4,722		4,722
Exercise of stock options (in shares)		176
Issuance of shares pursuant to vesting of restricted stock units		180
Net payments for stock issuances and buybacks	(32,464)		687		$ (33,151)
Net payments for stock issuances and buybacks (in shares)		(715)			715
Balance at Dec. 31, 2017	616,030	$ 22	307,821	434,766	$ (121,540)	(5,039)
Balance (in shares) at Dec. 31, 2017		18,662			3,357
Net income	61,400			61,400
Other comprehensive income (loss)	(6,683)					(6,683)
Equity compensation	11,506		11,328		$ 178
Exercise of stock options	5,842		5,842
Exercise of stock options (in shares)		209
Issuance of shares pursuant to vesting of restricted stock units		226			(8)
Net payments for stock issuances and buybacks	(17,125)		1,217		$ (18,342)
Net payments for stock issuances and buybacks (in shares)		(280)			280
Reclassification of stranded tax effects due to adoption of accounting principle				829		(829)
Dividends declared	(10,553)			(10,553)
Balance at Dec. 31, 2018	$ 660,417	$ 22	$ 326,208	$ 486,442	$ (139,704)	$ (12,551)
Balance (in shares) at Dec. 31, 2018		18,817			3,629