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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect upon adoption of new accounting standard (Note 1)			$ 0		$ 0
Shares at beginning of year (in shares) at Dec. 31, 2014		70,029				40,616
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividends, net of forfeitures (in shares)		497
Repurchases of common stock (in shares)						1,540
Shares tendered in payment of the exercise price of stock options (in shares)						0
Exercise of stock options (in shares)		32
Employee stock purchase plan (in shares)	(26)					(26)
Shares at end of year (in shares) at Dec. 31, 2015		70,558				42,130
Balance at beginning of year at Dec. 31, 2014		$ 700	412,642	$ (371)	125,378	$ (398,961)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividends, net of forfeitures		5	556
Exercise of stock options		0	381
Income tax benefit from stock-based compensation			551
Stock-based compensation expense			5,819
Repurchases of common stock						(38,058)
Shares tendered in payment of the exercise price of stock options						0
Employee stock purchase plan	$ 578		327			251
Defined benefit pension plans, net of tax benefit of $207 and $89, and tax expense of $429, respectively	689			689
Net income	42,824				42,824
Dividends, net of forfeitures ($0.48, $0.48 and $0.45 per share, respectively)					(13,106)
Balance at end of year at Dec. 31, 2015		$ 705	420,276	318	155,096	$ (436,768)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in fair value of interest rate swap, net of tax	$ 0			0
Cumulative effect upon adoption of new accounting standard (Note 1)			0		0
Issuance for stock-based compensation and dividends, net of forfeitures (in shares)		695
Repurchases of common stock (in shares)						2,370
Shares tendered in payment of the exercise price of stock options (in shares)						3
Exercise of stock options (in shares)		15
Employee stock purchase plan (in shares)	(34)					(34)
Shares at end of year (in shares) at Dec. 31, 2016		71,268				44,469
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividends, net of forfeitures		$ 8	447
Exercise of stock options		0	172
Income tax benefit from stock-based compensation			307
Stock-based compensation expense			6,705
Repurchases of common stock						$ (45,873)
Shares tendered in payment of the exercise price of stock options						(63)
Employee stock purchase plan	$ 669		305			364
Defined benefit pension plans, net of tax benefit of $207 and $89, and tax expense of $429, respectively	(134)			(134)
Net income	32,773				32,773
Dividends, net of forfeitures ($0.48, $0.48 and $0.45 per share, respectively)					(12,902)
Balance at end of year at Dec. 31, 2016	121,736	$ 713	428,212	184	174,967	$ (482,340)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in fair value of interest rate swap, net of tax	$ 0			0
Cumulative effect upon adoption of new accounting standard (Note 1)			769		(469)
Issuance for stock-based compensation and dividends, net of forfeitures (in shares)		221
Repurchases of common stock (in shares)						723
Shares tendered in payment of the exercise price of stock options (in shares)						0
Exercise of stock options (in shares)		5
Employee stock purchase plan (in shares)	(25)					(25)
Shares at end of year (in shares) at Dec. 31, 2017		71,494				45,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividends, net of forfeitures		$ 2	494
Exercise of stock options		0	72
Income tax benefit from stock-based compensation			0
Stock-based compensation expense			7,600
Repurchases of common stock						$ (17,010)
Shares tendered in payment of the exercise price of stock options						0
Employee stock purchase plan	$ 522		247			275
Defined benefit pension plans, net of tax benefit of $207 and $89, and tax expense of $429, respectively	(373)			(373)
Net income	33,285				33,285
Dividends, net of forfeitures ($0.48, $0.48 and $0.45 per share, respectively)					(12,640)
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]
Change in fair value of interest rate swap, net of tax	$ 289			$ 289