Statements of Stockholders' Equity (Unaudited) (USD $) In Thousands, except Share data	Total USD ($)	Number of Common Shares	Common Stock USD ($)	Retained Earnings USD ($)	Paid-in Capital USD ($)	Accumulated Other Comprehensive Income(Loss) USD ($)
Balance at Dec. 31, 2012	$ 444,323		$ 22	$ 346,866	$ 103,371	$ (5,936)
Balance, shares at Dec. 31, 2012		21,831,000
Net income	49,506			49,506
Other comprehensive (loss) income, net of tax	4,371					4,371
Proceeds from stock award exercises and issuances, shares		217,000
Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options			0
Proceeds from stock award exercises and issuances	(759)				(759)
Share-based compensation	2,174				2,174
Stock Repurchased During Period, Shares		(150,000)
Stock Repurchased During Period, Value	(7,118)				(7,118)
Excess tax benefits from exercise of stock options	2,849				2,849
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited		(5,000)
Restricted Stock Award, Forfeitures	(70)				(70)
Dividends declared	(31,857)			(31,857)
Balance at Dec. 31, 2013	463,419		22	364,515	100,447	(1,565)
Balance, shares at Dec. 31, 2013	21,893,137	21,893,000
Net income	34,813			34,813
Other comprehensive (loss) income, net of tax	(364)					(364)
Proceeds from stock award exercises and issuances, shares		66,000
Proceeds from stock award exercises and issuances	159				159
Share-based compensation	1,975				1,975
Stock Repurchased During Period, Shares		(112,000)
Stock Repurchased During Period, Value	(6,178)				(6,178)
Excess tax benefits from exercise of stock options	154				154
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited		(4,000)
Restricted Stock Award, Forfeitures	(203)				(203)
Dividends declared	(17,592)			(17,592)
Balance at Jun. 30, 2014	$ 476,183		$ 22	$ 381,736	$ 96,354	$ (1,929)
Balance, shares at Jun. 30, 2014	21,843,311	21,843,000