Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified		Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Deferred Compensation [Member]	Treasury Stock [Member]
Beginning Balances at Dec. 31, 2013		$ 278,773	$ 4,691	$ 152,341	$ 124,274	$ (2,533)	$ 1,124	$ (1,124)
Beginning Balances, shares at Dec. 31, 2013	[1]		14,457,345
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		36,092			36,092
Other comprehensive loss		(3,143)				(3,143)
Dividend declared, shares			0
Dividend declared ($0.27 and $1.067 per share for the first quarter of 2015 and for the year ended December 31, 2014 respectively)		(15,675)			(15,675)
Stock Issued During The Period Shares Retirement Savings Plan And Dividend Reinvestment Plan			43,367
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan		1,860	16	1,844
Conversion of debentures, shares	[1]		47,313
Conversion of debentures		535	15	520
Share-based compensation, shares	[1],[2],[3]		40,686
Share-based compensation and tax benefit	[2],[3]	1,889	13	1,876
Stock Split in Form of Stock Dividend Adjustment to Retained Earnings		(9)	2,365		(2,374)
Treasury stock activities		0					134	(134)
Ending Balances at Dec. 31, 2014		300,322	7,100	156,581	142,317	(5,676)	1,258	(1,258)
Ending Balances, shares at Dec. 31, 2014	[1]		14,588,711
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		21,109			21,109
Other comprehensive loss		108				108
Dividend declared, shares			8,059
Dividend declared ($0.27 and $1.067 per share for the first quarter of 2015 and for the year ended December 31, 2014 respectively)		(3,588)	4	388	(3,980)
Share-based compensation, shares	[1],[2],[3]		31,219
Share-based compensation and tax benefit	[2],[3]	(205)	15	(220)
Treasury stock activities		0					457	(457)
Ending Balances at Mar. 31, 2015		$ 317,746	$ 7,119	$ 156,749	$ 159,446	$ (5,568)	$ 1,715	$ (1,715)
Ending Balances, shares at Mar. 31, 2015	[1]		14,627,989

[1] Includes 53,442 and 53,125 shares at March 31, 2015 and December 31, 2014, respectively, held in a Rabbi Trust related to our Deferred Compensation Plan.

[2] The shares issued under the SICP are net of shares withheld for employee taxes. For the three months ended March 31, 2015 and for the year ended December 31, 2014, we withheld 12,620 and 12,687 shares, respectively, for taxes.

[3] Includes amounts for shares issued for Directors’ compensation.