CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Shares at beginning of year (in shares) at Dec. 31, 2016		71,268				44,469
Balance at beginning of year at Dec. 31, 2016	$ 121,736	$ 713	$ 428,212	$ 184	$ 174,967	$ (482,340)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	33,285				33,285
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)		221
Issuance for stock-based compensation and dividend equivalents, net of forfeitures	0	$ 2	494		(496)
Exercise of stock options (in shares)		5
Exercise of stock options	72		72
Stock-based compensation expense	$ 7,600		7,600
Employee stock purchase plan (in shares)	(25)					(25)
Employee stock purchase plan	$ 522		247			$ 275
Dividends	(12,144)				(12,144)
Defined benefit pension plans, net of tax	(373)			(373)
Change in fair value of interest rate swap, net of tax	289			289
Repurchases of common stock (in shares)						723
Repurchases of common stock	(17,010)					$ (17,010)
Shares at end of year (in shares) at Dec. 31, 2017		71,494				45,167
Balance at end of year at Dec. 31, 2017	134,277	$ 715	437,394	100	195,143	$ (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	$ 719	447,337	1,296	237,308	$ (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)
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	$ 722	$ 459,545	$ (1,526)	$ 350,545	$ (642,023)