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, 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 (in shares)		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 (in shares)		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
Net income	68,938			68,938
Other comprehensive income (loss)	407					407
Equity compensation	15,818		15,818
Exercise of stock options	2,924		2,924
Exercise of stock options (in shares)		94
Issuance of shares pursuant to vesting of restricted stock units	1	$ 1
Issuance of shares pursuant to vesting of restricted stock units (in shares)		306
Net payments for stock issuances and buybacks	(23,414)		1,845		$ (25,259)
Net payments for stock issuances and buybacks (in shares)		(349)			349
Dividends declared	(10,540)			(10,540)
Balance at Dec. 31, 2019	$ 714,551	$ 23	$ 346,795	$ 544,840	$ (164,963)	$ (12,144)
Balance (in shares) at Dec. 31, 2019		18,868			3,978