Loans and Allowance for Loan Losses (Details 2) (Acquired loans, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Loans and Allowance for Loan Losses
Total covered loans	$ 257,066	$ 282,728	$ 363,051
Total non-covered loans	738,189	792,014	6,093
Total acquired loans	995,255	1,074,742	369,144
Less allowance for acquired loan losses	(31,277)	(32,132)	(34,355)	(31,620)
Loans, net	963,978	1,042,610	334,789
Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	98,880	110,414	148,340
Total non-covered loans	120,149	131,555	2,962
Total acquired loans	219,029	241,969	151,302
Less allowance for acquired loan losses	(26,302)	(24,988)	(25,712)
Loans, net	192,727	216,981	125,590
Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	158,186	172,314	214,711
Total non-covered loans	547,806	587,244	3,131
Total acquired loans	776,226	832,773	217,842
Less allowance for acquired loan losses	(4,975)	(7,144)	(8,643)
Loans, net	771,251	825,629	209,199
Commercial loans greater than or equal to $1 million-CBT
Loans and Allowance for Loan Losses
Total covered loans	48,110	49,684	56,316
Total acquired loans	48,110		56,316
Less allowance for acquired loan losses	(14,956)	(15,408)	(16,851)	(16,706)
Commercial loans greater than or equal to $1 million-CBT | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	19,433	19,483	21,956
Commercial loans greater than or equal to $1 million-CBT | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	28,677	30,201	34,360
Commercial real estate
Loans and Allowance for Loan Losses
Total covered loans	52,972	62,962	99,834
Total non-covered loans	294,266	309,962	963
Total acquired loans	347,238		100,797
Less allowance for acquired loan losses	(842)	(1,517)	(1,391)	(1,318)
Commercial real estate | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	17,648	22,946	35,202
Total non-covered loans	49,391	53,259	353
Commercial real estate | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	35,324	40,016	64,632
Total non-covered loans	244,875	256,703	610
Commercial real estate construction and development
Loans and Allowance for Loan Losses
Total covered loans	27,657	32,575	44,256
Total non-covered loans	82,402	97,876	83
Total acquired loans	110,059		44,339
Less allowance for acquired loan losses	(2,484)	(1,628)	(2,057)
Commercial real estate construction and development | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	11,690	15,107	24,513
Total non-covered loans	27,431	32,975	22
Commercial real estate construction and development | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	15,967	17,468	19,743
Total non-covered loans	54,971	64,901	61
Residential real estate
Loans and Allowance for Loan Losses
Total covered loans	97,772	104,811	128,210
Total non-covered loans	238,258	250,316	979
Total acquired loans	336,030		129,189
Less allowance for acquired loan losses	(4,561)	(4,616)	(4,335)	(5,471)
Residential real estate | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	37,091	39,050	50,816
Total non-covered loans	39,027	40,585	342
Residential real estate | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	60,681	65,761	77,394
Total non-covered loans	199,231	209,731	637
Consumer
Loans and Allowance for Loan Losses
Total covered loans	3,845	4,324	6,145
Total non-covered loans	9,323	11,361	2,438
Total acquired loans	13,168		8,583
Less allowance for acquired loan losses	(89)	(96)	(10)
Consumer | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	776	948	2,057
Total non-covered loans	1,416	1,672	2,170
Consumer | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	3,069	3,376	4,088
Total non-covered loans	7,907	9,689	268
Commercial and industrial
Loans and Allowance for Loan Losses
Total covered loans	21,978	23,600	22,890
Total non-covered loans	43,706	49,284	1,630
Total acquired loans	65,684		24,520
Less allowance for acquired loan losses	(3,783)	(4,305)	(4,583)	(4,564)
Commercial and industrial | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	7,682	8,281	8,570
Total non-covered loans	2,884	3,064	75
Commercial and industrial | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	14,296	15,319	14,320
Total non-covered loans	40,822	46,220	1,555
Single pay
Loans and Allowance for Loan Losses
Total covered loans	4,732	4,772	5,400
Total acquired loans	4,732		5,400
Less allowance for acquired loan losses	(4,562)	(4,562)	(5,128)	(3,561)
Single pay | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	4,560	4,599	5,226
Single pay | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total covered loans	172	173	174
Total FASB ASC Topic 310-30 acquired loans
Loans and Allowance for Loan Losses
Total covered loans	257,066	282,728	282,728
Total non-covered loans	667,955	718,799	718,799
Total acquired loans	925,021	1,001,527	369,144
Less allowance for acquired loan losses	(31,277)	(32,132)	(34,355)
Loans, net	893,744	969,395	334,789	370,581
Total FASB ASC Topic 310-30 acquired loans | Loans Impaired at Acquisition
Loans and Allowance for Loan Losses
Total acquired loans	219,029	241,969	151,302
Less allowance for acquired loan losses	(26,302)	(24,988)	(25,712)
Loans, net	192,727	216,981	125,590	146,955
Total FASB ASC Topic 310-30 acquired loans | Loans Not Impaired at Acquisition
Loans and Allowance for Loan Losses
Total acquired loans	705,992	759,558	217,842
Less allowance for acquired loan losses	(4,975)	(7,144)	(8,643)
Loans, net	701,017	752,414	209,199	223,626
Total FASB ASC Topic 310-20 acquired loans (non-covered)
Loans and Allowance for Loan Losses
Total non-covered loans	70,234	73,215
Total acquired loans	70,234	73,215	73,215
Loans, net	$ 70,234	$ 73,215	$ 73,215