Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Stock	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Loss	Comprehensive Income
Balance at Dec. 31, 2008	$ 244,928		$ 28,127	$ 166,815	$ 59,171	$ (9,185)
Balance (in shares) at Dec. 31, 2008			11,250,603
Comprehensive income:
Net income	13,595				13,595		13,595
Other comprehensive income, net of tax effects
Pension and retiree medical plan	1,279					1,279	1,279
Change in pension liability for plan curtailment	1,283					1,283	1,283
Change in net unrealized gain on securities available for sale	4,795					4,795	4,795
Noncredit portion of other-than-temporary impairment losses recognized in earnings	(3,540)					(3,540)	(3,540)
Change in unrealized losses on derivative financial instruments qualifying as cash flow hedges	(14)					(14)	(14)
Total comprehensive income	17,398						17,398
Cash dividends on Series T preferred stock at annual dividend rate of 5%	(1,115)	3,559			(4,674)
Cash dividends declared at $.68 per share	(8,177)				(8,177)
Issuance of Series T preferred stock, net of issuance costs	64,632	61,220		3,412
Issuance of Series T preferred stock (in shares)		64,779
Repurchase of Series T preferred stock and warrants	(66,179)	(64,779)		(1,400)
Repurchase of Series T preferred stock and warrants (in shares)		(64,779)
Stock options exercised	532		77	455
Stock options exercised (in shares)			30,831
Employee stock purchases	566		70	496
Employee stock purchases (in shares)			27,991
Restricted stock awards			224	(224)
Restricted stock awards (in shares)			89,431
Common stock repurchased	(446)		(40)	(406)
Common stock repurchased (in shares)			(15,823)
Share-based compensation expense	1,431			1,431
Common stock issued in public offering	29,249		3,391	25,858
Common stock issued in public offering (in shares)			1,356,500
Balance at Dec. 31, 2009	282,819		31,849	196,437	59,915	(5,382)
Balance (in shares) at Dec. 31, 2009			12,739,533
Comprehensive income:
Net income	51,882				51,882		51,882
Other comprehensive income, net of tax effects
Pension and retiree medical plan	(514)					(514)	(514)
Change in net unrealized gain on securities available for sale	(1,041)					(1,041)	(1,041)
Noncredit portion of other-than-temporary impairment losses recognized in earnings	3,540					3,540	3,540
Change in unrealized losses on derivative financial instruments qualifying as cash flow hedges	(395)					(395)	(395)
Total comprehensive income	53,472						53,472
Cash dividends declared at $.68 per share	(8,680)				(8,680)
Stock options exercised	307		41	266
Stock options exercised (in shares)			16,220
Employee stock purchases	669		56	613
Employee stock purchases (in shares)			22,371
Restricted stock awards			57	(57)
Restricted stock awards (in shares)			22,971
Common stock repurchased	(255)		(18)	(237)
Common stock repurchased (in shares)			(7,272)
Share-based compensation expense	1,625			1,625
Balance at Dec. 31, 2010	329,957		31,985	198,647	103,117	(3,792)
Balance (in shares) at Dec. 31, 2010	12,793,823		12,793,823
Comprehensive income:
Net income	22,595				22,595		22,595
Other comprehensive income, net of tax effects
Pension and retiree medical plan	(3,007)					(3,007)	(3,007)
Change in net unrealized gain on securities available for sale	4,501					4,501	4,501
Change in unrealized losses on derivative financial instruments qualifying as cash flow hedges	(451)					(451)	(451)
Total comprehensive income	23,638						23,638
Cash dividends declared at $.68 per share	(9,514)				(9,514)
Stock options exercised	731		109	622
Stock options exercised (in shares)			43,533
Employee stock purchases	693		67	626
Employee stock purchases (in shares)			26,838
Restricted stock awards			144	(144)
Restricted stock awards (in shares)			57,641
Common stock repurchased	(342)		(29)	(313)
Common stock repurchased (in shares)			(11,445)
Share-based compensation expense	1,777			1,777
Common stock issued in private placement offering	34,840		2,823	32,017
Common stock issued in private placement offering (in shares)			1,129,032
Balance at Dec. 31, 2011	$ 381,780		$ 35,099	$ 233,232	$ 116,198	$ (2,749)
Balance (in shares) at Dec. 31, 2011	14,039,422		14,039,422