Loans and Asset Quality Information (Details 9) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Activity in the allowance for loan losses for non-covered loans
Provisions	$ 11,149	$ 21,555
Loans receivable:
Ending balance - total	2,131,360	2,093,184	2,092,819
Allowance Non-Covered Loans | Commercial, financial and agricultural
Loans receivable:
Ending balance - total	171,721	170,210	170,741
Allowance Non-Covered Loans | Real Estate construction, land development and other land loans
Loans receivable:
Ending balance - total	220,702	243,761	218,108
Allowance Non-Covered Loans | Real estate residential, farmland and mutli-family
Loans receivable:
Ending balance - total	828,273	809,205	819,439
Allowance Non-Covered Loans | Real estate home equity lines of credit
Loans receivable:
Ending balance - total	200,136	208,330	220,880
Allowance Non-Covered Loans | Real estate commercial
Loans receivable:
Ending balance - total	648,732	605,285	627,940
Allowance Non-Covered Loans | Consumer
Loans receivable:
Ending balance - total	51,796	56,393	55,711
Non-covered
Activity in the allowance for loan losses for non-covered loans
Beginning balance	41,643	35,610	35,610
Charge-offs	(4,795)	(8,255)
Recoveries	2,142	543
Provisions	5,771	18,557
Ending balance	44,761	46,455
Ending balances: Allowance for loan losses
Individually evaluated for impairment	2,124	8,559
Collectively evaluated for impairment	42,637	37,896
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment	26,020	66,717
Collectively evaluated for impairment	2,105,340	2,026,467
Loans acquired with deteriorated credit quality
Commercial, financial and agricultural
Activity in the allowance for loan losses for non-covered loans
Beginning balance	4,687	3,780	3,780
Charge-offs	(824)	(1,318)	(4,912)
Recoveries	19	16	354
Provisions	1,067	2,476	5,465
Ending balance	4,949	4,954	4,687
Ending balances: Allowance for loan losses
Individually evaluated for impairment	190	869
Collectively evaluated for impairment	4,759	4,085	4,687
Loans acquired with deteriorated credit quality
Loans receivable:
Ending balance - total	157,235	151,148	155,273
Ending balances: Loans
Individually evaluated for impairment	1,088	1,011
Collectively evaluated for impairment	170,633	169,199	170,741
Loans acquired with deteriorated credit quality
Real Estate construction, land development and other land loans
Activity in the allowance for loan losses for non-covered loans
Beginning balance	12,856	11,306	11,306
Charge-offs	(823)	(2,678)
Recoveries	593	188
Provisions	2,231	7,603
Ending balance	14,857	16,419
Ending balances: Allowance for loan losses
Individually evaluated for impairment	520	3,473
Collectively evaluated for impairment	14,337	12,946	12,856
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment	5,115	24,746	4,276
Collectively evaluated for impairment	215,587	219,015	213,832
Loans acquired with deteriorated credit quality
Real estate residential, farmland and mutli-family
Activity in the allowance for loan losses for non-covered loans
Beginning balance	14,082	13,532	13,532
Charge-offs	(797)	(2,091)	(20,879)
Recoveries	546	194	430
Provisions	1,454	3,734	20,999
Ending balance	15,285	15,369	14,082
Ending balances: Allowance for loan losses
Individually evaluated for impairment	259	1,926	50
Collectively evaluated for impairment	15,026	13,443	14,032
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment	2,257	14,366	1,705
Collectively evaluated for impairment	836,016	794,839	817,734
Loans acquired with deteriorated credit quality
Real estate home equity lines of credit
Activity in the allowance for loan losses for non-covered loans
Beginning balance	1,884	1,690	1,690
Charge-offs	(624)	(451)	(3,287)
Recoveries	58	34	209
Provisions	722	859	3,272
Ending balance	2,040	2,132	1,884
Ending balances: Allowance for loan losses
Individually evaluated for impairment		406
Collectively evaluated for impairment	2,040	1,726	1,884
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment		1,331
Collectively evaluated for impairment	200,136	206,999	200,880
Loans acquired with deteriorated credit quality
Real estate commercial
Activity in the allowance for loan losses for non-covered loans
Beginning balance	5,247	3,414	3,414
Charge-offs	(540)	(1,365)	(16,616)
Recoveries	789	41	333
Provisions	218	3,647	18,116
Ending balance	5,714	5,737	5,247
Ending balances: Allowance for loan losses
Individually evaluated for impairment	1,155	1,885	957
Collectively evaluated for impairment	4,559	3,852	4,290
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment	17,560	25,263	15,040
Collectively evaluated for impairment	631,172	580,022	612,900
Loans acquired with deteriorated credit quality
Consumer
Activity in the allowance for loan losses for non-covered loans
Beginning balance	1,939	1,872	1,872
Charge-offs	(528)	(352)	(1,539)
Recoveries	137	70	273
Provisions	243	236	1,333
Ending balance	1,791	1,826	1,939
Ending balances: Allowance for loan losses
Individually evaluated for impairment
Collectively evaluated for impairment	1,791	1,826	1,939
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment
Collectively evaluated for impairment	51,796	56,393	55,711
Loans acquired with deteriorated credit quality
Unallocated
Activity in the allowance for loan losses for non-covered loans
Beginning balance	948	16	16
Charge-offs	(659)
Recoveries
Provisions	(164)	2	932
Ending balance	125	18	948
Ending balances: Allowance for loan losses
Individually evaluated for impairment
Collectively evaluated for impairment	125	18	948
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment
Collectively evaluated for impairment
Loans acquired with deteriorated credit quality
Real Estate construction, land development and other land loans
Activity in the allowance for loan losses for non-covered loans
Beginning balance		11,306	11,306
Charge-offs			(19,312)
Recoveries			986
Provisions			19,876
Ending balance			12,856
Ending balances: Allowance for loan losses
Individually evaluated for impairment
Collectively evaluated for impairment			12,856
Loans acquired with deteriorated credit quality
Loans receivable:
Ending balance - total	253,275	287,833	251,569
Ending balances: Loans
Individually evaluated for impairment			4,276
Collectively evaluated for impairment			213,832
Loans acquired with deteriorated credit quality
Non-covered
Activity in the allowance for loan losses for non-covered loans
Beginning balance		35,610	35,610
Charge-offs			(66,545)
Recoveries			2,585
Provisions			69,993
Ending balance			41,643
Ending balances: Allowance for loan losses
Individually evaluated for impairment			1,007
Collectively evaluated for impairment			40,636
Loans acquired with deteriorated credit quality
Ending balances: Loans
Individually evaluated for impairment			21,021
Collectively evaluated for impairment			2,071,798
Loans acquired with deteriorated credit quality