Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Balances, value at Dec. 31, 2013	$ 1,227,033	$ 5,383	$ 644,594	$ 586,422	$ (9,094)	$ (272)
Balances, shares at Dec. 31, 2013	53,825	53,825
Stock-based compensation expense	1,359		1,359
Shares repurchased and retired, shares		(196)
Shares repurchased and retired, value	(4,537)	(20)	(2,117)	(2,400)
Stock options exercised, shares	304	304
Stock options exercised, value	5,811	30	5,781
Issuance of restricted shares, net of forfeitures, shares		86
Issuance of restricted shares, net of forfeitures, value	0	9	(9)
Restricted shares withheld for taxes, shares		(13)
Restricted shares withheld for taxes	(309)	(1)	(308)
Excess tax benefit of stock-based compensation	236		236
Comprehensive income	19,081			19,125	(44)
Balances, value at Mar. 31, 2014	$ 1,248,674	$ 5,401	$ 649,536	$ 603,147	$ (9,138)	$ (272)
Balances, shares at Mar. 31, 2014	54,006	54,006