Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Common Stock Held in Treasury	Accumulated Other Comprehensive Income.	Total
Balance at Dec. 31, 2012	$ 520	$ 245,002	$ 405,485	$ (253,111)	$ 11,874	$ 409,770
Increase (Decrease) in Stockholders' Equity
Net income			31,085			31,085
Other comprehensive loss					(3,338)	(3,338)
Issuance of common stock for restricted stock unit (1,203,142 shares), (1,123,720 shares) and (1,159,047 shares), and employee stock unit awards (0 shares), (14,228 shares) and (39,002 shares), including tax benefit shortfall and award cancellations of $1.5 million, and excess tax benefit of$0.6, $2.1 million, respectively for year end 2013, 2014, and 2015 respectively.		(19,774)		17,559		(2,215)
Issuance of common stock for the employee stock purchase plan (121,363 shares), (71,587 shares) and (70,924 shares), respectively for year end 2013, 2014, and 2015 respectively	2	933				935
Shares withheld for net settlements of share-based awards (352,051 shares), (367,367 shares), (418,135 shares), respectively for year end 2013, 2014, and 2015 respectively				(4,532)		(4,532)
Purchase of common stock for treasury (2,005,200 shares), (2,671,637 shares), and (1,992,831 shares), respectively for year end 2013, 2014, and 2015 respectively				(28,169)		(28,169)
Share-based compensation		13,896				13,896
Balance at Dec. 31, 2013	522	240,057	436,570	(268,253)	8,536	417,432
Increase (Decrease) in Stockholders' Equity
Net income			50,892			50,892
Other comprehensive loss					(14,430)	(14,430)
Issuance of common stock for restricted stock unit (1,203,142 shares), (1,123,720 shares) and (1,159,047 shares), and employee stock unit awards (0 shares), (14,228 shares) and (39,002 shares), including tax benefit shortfall and award cancellations of $1.5 million, and excess tax benefit of$0.6, $2.1 million, respectively for year end 2013, 2014, and 2015 respectively.		(16,244)		16,020		(224)
Issuance of common stock for the employee stock purchase plan (121,363 shares), (71,587 shares) and (70,924 shares), respectively for year end 2013, 2014, and 2015 respectively		963				963
Shares withheld for net settlements of share-based awards (352,051 shares), (367,367 shares), (418,135 shares), respectively for year end 2013, 2014, and 2015 respectively				(6,231)		(6,231)
Purchase of common stock for treasury (2,005,200 shares), (2,671,637 shares), and (1,992,831 shares), respectively for year end 2013, 2014, and 2015 respectively				(48,165)		(48,165)
Share-based compensation		15,359				15,359
Balance at Dec. 31, 2014	522	240,135	487,462	(306,629)	(5,894)	415,596
Increase (Decrease) in Stockholders' Equity
Net income			91,570			91,570
Other comprehensive loss					(13,601)	(13,601)
Issuance of common stock for restricted stock unit (1,203,142 shares), (1,123,720 shares) and (1,159,047 shares), and employee stock unit awards (0 shares), (14,228 shares) and (39,002 shares), including tax benefit shortfall and award cancellations of $1.5 million, and excess tax benefit of$0.6, $2.1 million, respectively for year end 2013, 2014, and 2015 respectively.		(20,299)		20,621		322
Issuance of common stock for the employee stock purchase plan (121,363 shares), (71,587 shares) and (70,924 shares), respectively for year end 2013, 2014, and 2015 respectively	1	1,166				1,167
Shares withheld for net settlements of share-based awards (352,051 shares), (367,367 shares), (418,135 shares), respectively for year end 2013, 2014, and 2015 respectively				(8,978)		(8,978)
Purchase of common stock for treasury (2,005,200 shares), (2,671,637 shares), and (1,992,831 shares), respectively for year end 2013, 2014, and 2015 respectively				(42,046)		(42,046)
Dividend declared on common stock		2	(7,406)	109		(7,295)
Share-based compensation		18,086				18,086
Balance at Dec. 31, 2015	$ 523	$ 239,090	$ 571,626	$ (336,923)	$ (19,495)	$ 454,821