Condensed Consolidated Statement Of Stockholders' Equity (USD $) In Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings	Treasury Stock
Balance - at Dec. 31, 2011	$ 277,296	$ 248	$ 84,389	$ 222,126	$ (29,467)
Net income	37,340			37,340
Issuance of shares of common stock pursuant to stock options, deferred stock units and restricted stock	7,859	6	7,853
Income tax benefit relating to issuance of common stock pursuant to stock-based awards	270		270
Stock-based compensation expense	6,318		6,318
Issuance of deferred stock units relating to prior year compensation	200		200
Special cash dividend ($2.00 per share)	(45,038)			(45,038)
Dividend equivalents on stock-based awards			1,382	(1,382)
Balance - at Dec. 31, 2012	284,245	254	100,412	213,046	(29,467)
Net income	50,119			50,119
Issuance of shares of common stock pursuant to stock options, deferred stock units and restricted stock	13,447	7	13,440
Income tax benefit relating to issuance of common stock pursuant to stock-based awards	1,534		1,534
Stock-based compensation expense	10,839		10,839
Issuance of deferred stock units relating to prior year compensation	135		135
Special cash dividend ($2.00 per share)	(46,706)			(46,706)
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)
Balance - at Dec. 31, 2014	$ 394,898	$ 265	$ 147,186	$ 276,914	$ (29,467)