Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative-Effect Adjustments for Adoption of Accounting Principle	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative-Effect Adjustments for Adoption of Accounting Principle	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative-Effect Adjustments for Adoption of Accounting Principle	[1]
Balance at Dec. 31, 2017	$ 616,030		$ 22	$ 307,821	$ 434,766		$ (121,540)	$ (5,039)	$ (829)
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
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)
Balance at Dec. 31, 2018	660,417		$ 22	326,208	486,442		$ (139,704)	(12,551)
Dividends declared	(10,553)				(10,553)
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
Balance at Dec. 31, 2019	714,551		$ 23	346,795	544,840		$ (164,963)	(12,144)
Dividends declared	(10,540)				(10,540)
Balance (in shares) at Dec. 31, 2019			18,868				3,978
Net income	54,959				54,959
Other comprehensive income (loss)	(1,962)							(1,962)
Equity compensation	17,555			17,555
Exercise of stock options	2,652			2,652
Exercise of stock options (in shares)			70
Issuance of shares pursuant to vesting of restricted stock units (in shares)			389
Net payments for stock issuances and buybacks	(29,726)			2,056			$ (31,782)
Net payments for stock issuances and buybacks (in shares)			(417)				417
Balance at Dec. 31, 2020	746,961	$ (513)	$ 23	$ 369,058	588,731	$ (513)	$ (196,745)	$ (14,106)
Accounting Standards Update Extensible List		us-gaap:AccountingStandardsUpdate201613Member				us-gaap:AccountingStandardsUpdate201613Member
Dividends declared	$ (10,555)				$ (10,555)
Balance (in shares) at Dec. 31, 2020			18,910				4,395

[1] The Company has adjusted the balance of accumulated other comprehensive (loss) income at December 3, 2017 after the adoption of ASU 2018-02.