Consolidated Statements of Changes in Shareholders' Equity (USD $)	Total	Preferred Stock	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Comprehensive Income
Balance at Dec. 31, 2009	$ 282,819,000	$ 0	$ 31,849,000	$ 196,437,000	$ 59,915,000	$ (5,382,000)
Balance (in shares) at Dec. 31, 2009		0	12,739,533
Comprehensive income:
Net income	51,882,000				51,882,000		51,882,000
Other comprehensive income, net of tax effects	1,590,000					1,590,000	1,590,000
Comprehensive income	53,472,000						53,472,000
Cash dividends declared at $.69, $.68 and $.68 per share for the years ending December 31, 2012, 2011 and 2010, respectively	(8,680,000)				(8,680,000)
Stock options exercised	307,000		41,000	266,000
Stock options exercised (in shares)			16,220
Employee stock purchases	669,000		56,000	613,000
Employee stock purchases (in shares)			22,371
Restricted stock awards			57,000	(57,000)
Restricted stock awards (in shares)			22,971
Common stock repurchased	(255,000)		(18,000)	(237,000)
Common stock repurchased (in shares)			(7,272)
Share-based compensation expense	1,625,000			1,625,000
Balance at Dec. 31, 2010	329,957,000		31,985,000	198,647,000	103,117,000	(3,792,000)
Balance (in shares) at Dec. 31, 2010			12,793,823
Comprehensive income:
Net income	22,595,000				22,595,000		22,595,000
Other comprehensive income, net of tax effects	1,043,000					1,043,000	1,043,000
Comprehensive income	23,638,000						23,638,000
Cash dividends declared at $.69, $.68 and $.68 per share for the years ending December 31, 2012, 2011 and 2010, respectively	(9,514,000)				(9,514,000)
Stock options exercised	731,000		109,000	622,000
Stock options exercised (in shares)			43,533
Employee stock purchases	693,000		67,000	626,000
Employee stock purchases (in shares)			26,838
Restricted stock awards			144,000	(144,000)
Restricted stock awards (in shares)			57,641
Common stock repurchased	(342,000)		(29,000)	(313,000)
Common stock repurchased (in shares)			(11,445)
Share-based compensation expense	1,777,000			1,777,000
Common stock issued in private placement offering	34,840,000		2,823,000	32,017,000
Common stock issued in private placement offering (in shares)			1,129,032
Balance at Dec. 31, 2011	381,780,000		35,099,000	233,232,000	116,198,000	(2,749,000)
Balance (in shares) at Dec. 31, 2011	14,039,422		14,039,422
Comprehensive income:
Net income	30,032,000				30,032,000		30,032,000
Other comprehensive income, net of tax effects	3,125,000					3,125,000	3,125,000
Comprehensive income	33,157,000						33,157,000
Cash dividends declared at $.69, $.68 and $.68 per share for the years ending December 31, 2012, 2011 and 2010, respectively	(10,244,000)				(10,244,000)
Stock options exercised	1,244,000		129,000	1,115,000
Stock options exercised (in shares)			51,887
Employee stock purchases	720,000		55,000	665,000
Employee stock purchases (in shares)			22,135
Restricted stock awards			106,000	(106,000)
Restricted stock awards (in shares)			42,674
Common stock repurchased	(836,000)		(58,000)	(778,000)
Common stock repurchased (in shares)			(23,532)
Share-based compensation expense	1,741,000			1,741,000
Common stock issued for the Peoples acquisition	31,145,000		2,507,000	28,638,000
Common stock issued for the Peoples acquisition (in shares)			1,002,741
Common stock issued for the Savannah acquisition	68,842,000		4,506,000	64,336,000
Common stock issued for the Savannah acquisition (in shares)			1,802,137
Balance at Dec. 31, 2012	$ 507,549,000		$ 42,344,000	$ 328,843,000	$ 135,986,000	$ 376,000
Balance (in shares) at Dec. 31, 2012	16,937,464		16,937,464