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 period (in shares) at Dec. 31, 2012		68,531				33,980
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)		882
Exercise of stock options (in shares)	67	67
Shares tendered in payment of the exercise price of stock options (in shares)						0
Repurchases of common stock (in shares)						1,812
Employee stock purchase plan (in shares)	(41)					(41)
Shares at end of period (in shares) at Dec. 31, 2013		69,480				35,751
Balance at beginning of period at Dec. 31, 2012		$ 685	$ 400,688	$ (2,713)	$ 40,203	$ (269,017)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividend equivalents, net of forfeitures		9	72
Exercise of stock options		1	597
Income tax benefit from stock-based compensation			399
Stock-based compensation expense			2,570
Employee stock purchase plan	$ 613		274			339
Pension and post-retirement plans, net of tax of $429, $394 and $1,919, respectively	3,030			3,030
Net income	$ 10,787				10,787
Dividends and dividend equivalents, net of forfeitures ($0.45, $0.41 and $0.10 per share, respectively)					(3,378)
Repurchases of common stock						(27,313)
Shares tendered in payment of the exercise price of stock options						0
Balance at end of period at Dec. 31, 2013		$ 695	404,600	317	47,612	$ (295,991)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)		444
Exercise of stock options (in shares)	105	105
Shares tendered in payment of the exercise price of stock options (in shares)						4
Repurchases of common stock (in shares)						4,896
Employee stock purchase plan (in shares)	(35)					(35)
Shares at end of period (in shares) at Dec. 31, 2014		70,029				40,616
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividend equivalents, net of forfeitures		$ 4	369
Exercise of stock options		1	1,213
Income tax benefit from stock-based compensation			595
Stock-based compensation expense			5,475
Employee stock purchase plan	$ 699		390			$ 309
Pension and post-retirement plans, net of tax of $429, $394 and $1,919, respectively	(688)			(688)
Net income	90,915				90,915
Dividends and dividend equivalents, net of forfeitures ($0.45, $0.41 and $0.10 per share, respectively)					(13,149)
Repurchases of common stock						(103,195)
Shares tendered in payment of the exercise price of stock options						(84)
Balance at end of period at Dec. 31, 2014	$ 139,388	$ 700	412,642	(371)	125,378	$ (398,961)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividend equivalents, net of forfeitures (in shares)		497
Exercise of stock options (in shares)	32	32
Shares tendered in payment of the exercise price of stock options (in shares)						0
Repurchases of common stock (in shares)						1,540
Employee stock purchase plan (in shares)	(26)					(26)
Shares at end of period (in shares) at Dec. 31, 2015		70,558				42,130
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance for stock-based compensation and dividend equivalents, 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
Employee stock purchase plan	$ 578		327			$ 251
Pension and post-retirement plans, net of tax of $429, $394 and $1,919, respectively	689			689
Net income	42,824				42,824
Dividends and dividend equivalents, net of forfeitures ($0.45, $0.41 and $0.10 per share, respectively)					(13,106)
Repurchases of common stock						(38,058)
Shares tendered in payment of the exercise price of stock options						0
Balance at end of period at Dec. 31, 2015	$ 139,627	$ 705	$ 420,276	$ 318	$ 155,096	$ (436,768)