Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data		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, 2011		$ 240,780	$ 4,656	$ 149,403	$ 91,248	$ (4,527)	$ 817	$ (817)
Beginning Balances, shares at Dec. 31, 2011	[1]		9,567,307
Net Income		28,863			28,863
Other comprehensive loss/income		(535)				(535)
Dividend Reinvestment Plan		(7)		(7)
Dividend Reinvestment Plan, shares	[1]
Conversion of debentures		186	5	181
Conversion of debentures, shares	[1]		10,975
Share-based compensation	[2],[3]	1,011	10	1,001
Share-based compensation, shares	[1],[2],[3]		19,217
Tax benefit on share-based compensation		172		172
Deferred Compensation Plan							165	(165)
Purchase of treasury stock		(45)						(45)
Purchase of treasury stock, shares	[1]		(1,019)
Sale and distribution of treasury stock		45						45
Sale and distribution of treasury stock, shares	[1]		1,019
Dividends on share-based compensation		(64)			(64)
Cash dividends	[4]	(13,808)			(13,808)
Ending Balances at Dec. 31, 2012		256,598	4,671	150,750	106,239	(5,062)	982	(982)
Ending Balances, shares at Dec. 31, 2012	[1]		9,597,499
Net Income		14,869			14,869
Other comprehensive loss/income		49				49
Dividend Reinvestment Plan		(2)		(2)
Dividend Reinvestment Plan, shares	[1]
Conversion of debentures		45	1	44
Conversion of debentures, shares	[1]		2,642
Share-based compensation	[2],[3]	(258)	7	(265)
Share-based compensation, shares	[1],[2],[3]		13,921
Deferred Compensation Plan							12	(12)
Purchase of treasury stock		(12)						(12)
Purchase of treasury stock, shares	[1]		(261)
Sale and distribution of treasury stock		12						12
Sale and distribution of treasury stock, shares	[1]		261
Dividends on share-based compensation		(25)			(25)
Cash dividends	[4]	(3,504)			(3,504)
Ending Balances at Mar. 31, 2013		$ 267,772	$ 4,679	$ 150,527	$ 117,579	$ (5,013)	$ 994	$ (994)
Ending Balances, shares at Mar. 31, 2013	[1]		9,614,062

[1] Includes 33,722 and 33,461 shares at March 31, 2013 and December 31, 2012, respectively, held in a Rabbi Trust established by the Company relating to the Deferred Compensation Plan.

[2] Includes amounts for shares issued for Directors' compensation.

[3] The shares issued under the Performance Incentive Plan ("PIP") are net of shares withheld for employee taxes. For three months ended March 31, 2013 and for the year ended December 31, 2012, the Company withheld 10,411 and 5,670 shares, respectively, for taxes.

[4] Cash dividends per share for the periods ended March 31, 2013 and December 31, 2012 were $0.365 and $1.440, respectively.