Loans and Allowance for Loan Losses (Details 2) (Acquired loans, USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Loans and Allowance for Loan Losses
Total covered loans	$ 309,034		$ 394,495	$ 426,998
Total non-covered loans	211,957		7,706	8,763
Total acquired loans	520,991		402,201	435,761
Less allowance for acquired loan losses	(31,138)	(35,813)	(31,620)	(29,870)	(25,545)
Loans, net	489,853		370,581	405,891		321,038
Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	125,564		167,334	184,629
Total non-covered loans	27,227		3,496	4,365
Total acquired loans	152,791		170,830	188,994
Less allowance for acquired loan losses	(24,828)		(23,875)	(25,438)
Loans, net	127,963		146,955	163,556		143,059
Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	183,470		227,161	242,369
Total non-covered loans	184,730		4,210	4,398
Total acquired loans	368,200		231,371	246,767
Less allowance for acquired loan losses	(6,310)		(7,745)	(4,432)
Loans, net	361,890		223,626	242,335		177,979
Commercial loans greater than or equal to $1 million-CBT
Loans and Allowance for Loan Losses
Total covered loans	53,301		60,829	63,066
Total acquired loans	53,301			63,066
Less allowance for acquired loan losses	(15,812)	(16,871)	(16,706)	(18,559)	(16,807)
Commercial loans greater than or equal to $1 million-CBT | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	20,312		24,073	23,593
Commercial loans greater than or equal to $1 million-CBT | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	32,989		36,756	39,473
Commercial real estate
Loans and Allowance for Loan Losses
Total covered loans	74,757		107,465	115,889
Total non-covered loans	76,687		862	917
Total acquired loans	151,444			116,806
Less allowance for acquired loan losses	(447)	(1,812)	(1,318)	(1,318)	(1,318)
Commercial real estate | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	28,698		39,685	44,202
Total non-covered loans	11,202		305	300
Commercial real estate | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	46,059		67,780	71,687
Total non-covered loans	65,485		557	617
Commercial real estate construction and development
Loans and Allowance for Loan Losses
Total covered loans	36,435		50,953	60,610
Total non-covered loans	21,882		52	76
Total acquired loans	58,317			60,686
Less allowance for acquired loan losses	(1,494)	(3,238)
Commercial real estate construction and development | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	18,415		29,528	38,096
Total non-covered loans	6,582		5	28
Commercial real estate construction and development | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	18,020		21,425	22,514
Total non-covered loans	15,300		47	48
Residential real estate
Loans and Allowance for Loan Losses
Total covered loans	109,377		129,590	134,525
Total non-covered loans	96,064		1,183	943
Total acquired loans	205,441			135,468
Less allowance for acquired loan losses	(4,456)	(4,415)	(5,471)	(1,926)	(1,926)
Residential real estate | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	42,481		52,727	55,878
Total non-covered loans	5,734		244	250
Residential real estate | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	66,896		76,863	78,647
Total non-covered loans	90,330		939	693
Consumer
Loans and Allowance for Loan Losses
Total covered loans	4,957		5,096	8,006
Total non-covered loans	5,168		2,800	3,766
Total acquired loans	10,125			11,772
Less allowance for acquired loan losses	(89)	(73)
Consumer | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	1,257		2,669	3,074
Total non-covered loans	1,469		2,723	3,464
Consumer | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	3,700		2,427	4,932
Total non-covered loans	3,699		77	302
Commercial and industrial
Loans and Allowance for Loan Losses
Total covered loans	25,343		36,502	40,960
Total non-covered loans	12,156		2,809	3,061
Total acquired loans	37,499			44,021
Less allowance for acquired loan losses	(4,271)	(4,749)	(4,564)	(4,502)	(1,929)
Commercial and industrial | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	9,707		14,800	16,054
Total non-covered loans	2,240		219	323
Commercial and industrial | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	15,636		21,702	24,906
Total non-covered loans	9,916		2,590	2,738
Single pay
Loans and Allowance for Loan Losses
Total covered loans	4,864		4,060	3,942
Total acquired loans	4,864			3,942
Less allowance for acquired loan losses	(4,569)	(4,655)	(3,561)	(3,565)	(3,565)
Single pay | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	4,694		3,852	3,732
Single pay | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	$ 170		$ 208	$ 210