Condensed Consolidated Statement Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2013	$ 313,613	$ 261	$ 126,360		$ 216,459	$ (29,467)
Net income	62,266				62,266
Issuance of shares of common stock pursuant to stock options, deferred stock units and restricted stock	2,302	4	2,298
Income tax benefit relating to issuance of common stock pursuant to stock-based awards	3,914		3,914
Stock-based compensation expense	10,817		10,817
Issuance of deferred stock units relating to prior year compensation	1,986		1,986
Dividend equivalents on stock-based awards			1,811		(1,811)
Ending Balance at Dec. 31, 2014	394,898	265	147,186		276,914	(29,467)
Net income	74,345				74,345
Issuance of shares of common stock pursuant to stock options, deferred stock units and restricted stock	(7,558)	5	(7,563)
Income tax benefit relating to issuance of common stock pursuant to stock-based awards	9,028		9,028
Stock-based compensation expense	14,043		14,043
Issuance of deferred stock units relating to prior year compensation	2,046		2,046
Cash dividend					(48,227)
Dividend equivalents on stock-based awards			1,826		(1,826)
Ending Balance at Dec. 31, 2015	438,575	270	166,566		301,206	(29,467)
Net income	129,671				129,671
Issuance of shares of common stock pursuant to stock options, deferred stock units and restricted stock	(5,409)	4	(5,413)
Income tax benefit relating to issuance of common stock pursuant to stock-based awards	7,983		7,983
Stock-based compensation expense	15,420		15,420
Issuance of deferred stock units relating to prior year compensation	264		264
Other comprehensive loss				$ (1,798)
Cash dividend	(34,437)				(34,437)
Dividend equivalents on stock-based awards			1,161		(1,161)
Ending Balance at Dec. 31, 2016	$ 550,269	$ 274	$ 185,981		$ 395,279	$ (29,467)