CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Shares at beginning of year (in shares) at Dec. 31, 2017			71,494						45,167
Balance at beginning of year at Dec. 31, 2017	$ 134,277	$ (179)	$ 715	$ 437,394	$ 100		$ 195,143	$ (179)	$ (499,075)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57,980						57,980
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)			357
Issuance for stock-based compensation and dividend equivalents, net of forfeitures	0		$ 4	762			(766)
Exercise of stock options (in shares)			5						1
Exercise of stock options	0			46					$ (46)
Stock-based compensation expense	$ 8,797			8,797
Employee stock purchase plan (in shares)	(19)								(19)
Employee stock purchase plan	$ 549			338					$ 211
Dividends	(14,870)						(14,870)
Defined benefit pension plans, net of tax	881				881
Change in fair value of interest rate swap, net of tax	315				315
Repurchases of common stock (in shares)									673
Repurchases of common stock	(19,419)								$ (19,419)
Shares at end of year (in shares) at Dec. 31, 2018			71,856						45,822
Balance at end of year at Dec. 31, 2018	168,331	0	$ 719	447,337	1,296	$ 168	237,308	(168)	$ (518,329)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	130,862						130,862
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)			346
Issuance for stock-based compensation and dividend equivalents, net of forfeitures	0		$ 3	846			(849)
Exercise of stock options (in shares)			0						0
Exercise of stock options	0			0					$ 0
Stock-based compensation expense	$ 11,007			11,007
Employee stock purchase plan (in shares)	(17)								(17)
Employee stock purchase plan	$ 558			355					$ 203
Dividends	(16,608)						(16,608)
Defined benefit pension plans, net of tax	(2,183)				(2,183)
Change in fair value of interest rate swap, net of tax	(807)				(807)
Repurchases of common stock (in shares)									3,472
Repurchases of common stock	(123,897)								$ (123,897)
Shares at end of year (in shares) at Dec. 31, 2019			72,202						49,277
Balance at end of year at Dec. 31, 2019	167,263	$ (214)	$ 722	459,545	(1,526)		350,545	$ (214)	$ (642,023)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	56,039						56,039
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)			398
Issuance for stock-based compensation and dividend equivalents, net of forfeitures	0		$ 4	934			(938)
Stock-based compensation expense	$ 11,595			11,595
Employee stock purchase plan (in shares)	(19)								(19)
Employee stock purchase plan	$ 549			304					$ 245
Dividends	(16,787)						(16,787)
Defined benefit pension plans, net of tax	(1,706)				(1,706)
Change in fair value of interest rate swap, net of tax	(1,191)				(1,191)
Repurchases of common stock (in shares)									1,169
Repurchases of common stock	(35,613)								$ (35,613)
Shares at end of year (in shares) at Dec. 31, 2020			72,600						50,427
Balance at end of year at Dec. 31, 2020	$ 179,935		$ 726	$ 472,378	$ (4,423)		$ 388,645		$ (677,391)