Loans and the Allowance for Loan Losses (Details 10) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Rollforward of the allowance for loan losses
Beginning balance					$ 47,665						$ 44,347		$ 47,665		$ 44,347		$ 44,340
Charge-offs													(13,859)		(9,551)		(20,555)
Recoveries													2,316		2,519		2,437
Net charge-offs													(11,543)		(7,032)		(18,118)
Provision for loan losses													10,917		11,738		28,272
Benefit attributable to FDIC loss-share agreements													(6,278)		(2,361)		(10,408)
Recoveries payable to FDIC													1,528		973		261
Provision for loan losses charged to operations	1,050		2,217	1,450	1,450		2,000		2,300	3,000	3,050		6,167		10,350		18,125
Ending balance	42,289						47,665						42,289		47,665		44,347
Period-End Amount Allocated to:
Individually evaluated for impairment	10,762						14,650						10,762		14,650		17,597
Collectively evaluated for impairment	31,527						33,015						31,527		33,015		26,750
Acquired with deteriorated credit quality	0						0						0		0		0
Ending balance	42,289						47,665						42,289		47,665		44,347
Commercial, financial, agricultural
Rollforward of the allowance for loan losses
Beginning balance					3,090						3,307		3,090		3,307		4,197
Charge-offs													(1,516)		(1,184)		(4,923)
Recoveries													455		356		531
Net charge-offs													(1,061)		(828)		(4,392)
Provision for loan losses													1,297		982		4,274
Benefit attributable to FDIC loss-share agreements													(204)		(403)		(777)
Recoveries payable to FDIC													183		32		5
Provision for loan losses charged to operations													1,276		611		3,502
Ending balance	3,305						3,090						3,305		3,090		3,307
Period-End Amount Allocated to:
Individually evaluated for impairment	171						260						171		260		708
Collectively evaluated for impairment	3,134						2,830						3,134		2,830		2,599
Acquired with deteriorated credit quality	0						0						0		0		0
Ending balance	3,305						3,090						3,305		3,090		3,307
Real estate – construction
Rollforward of the allowance for loan losses
Beginning balance					1,091						711		1,091		711		1,073
Charge-offs													0		0		(187)
Recoveries													33		75		34
Net charge-offs													33		75		(153)
Provision for loan losses													290		304		(121)
Benefit attributable to FDIC loss-share agreements													0		0		(88)
Recoveries payable to FDIC													1		1		0
Provision for loan losses charged to operations													291		305		(209)
Ending balance	1,415						1,091						1,415		1,091		711
Period-End Amount Allocated to:
Individually evaluated for impairment	0						0						0		0		0
Collectively evaluated for impairment	1,415						1,091						1,415		1,091		711
Acquired with deteriorated credit quality	0						0						0		0		0
Ending balance	1,415						1,091						1,415		1,091		711
Real estate – 1-4 family mortgage
Rollforward of the allowance for loan losses
Beginning balance					18,629						18,347		18,629		18,347		17,191
Charge-offs													(5,662)		(3,093)		(9,231)
Recoveries													1,325		1,044		1,330
Net charge-offs													(4,337)		(2,049)		(7,901)
Provision for loan losses													(452)		2,496		13,201
Benefit attributable to FDIC loss-share agreements													(816)		(1,039)		(4,326)
Recoveries payable to FDIC													525		874		182
Provision for loan losses charged to operations													(743)		2,331		9,057
Ending balance	13,549						18,629						13,549		18,629		18,347
Period-End Amount Allocated to:
Individually evaluated for impairment	4,824						7,353						4,824		7,353		9,201
Collectively evaluated for impairment	8,725						11,276						8,725		11,276		9,146
Acquired with deteriorated credit quality	0						0						0		0		0
Ending balance	13,549						18,629						13,549		18,629		18,347
Real estate – commercial mortgage
Rollforward of the allowance for loan losses
Beginning balance					23,688						21,416		23,688		21,416		20,979
Charge-offs													(6,186)		(4,782)		(5,828)
Recoveries													436		980		455
Net charge-offs													(5,750)		(3,802)		(5,373)
Provision for loan losses													9,260		6,927		10,938
Benefit attributable to FDIC loss-share agreements													(5,258)		(919)		(5,202)
Recoveries payable to FDIC													819		66		74
Provision for loan losses charged to operations													4,821		6,074		5,810
Ending balance	22,759						23,688						22,759		23,688		21,416
Period-End Amount Allocated to:
Individually evaluated for impairment	5,767						7,036						5,767		7,036		7,688
Collectively evaluated for impairment	16,992						16,652						16,992		16,652		13,728
Acquired with deteriorated credit quality	0						0						0		0		0
Ending balance	22,759						23,688						22,759		23,688		21,416
Installment loans to individuals
Rollforward of the allowance for loan losses
Beginning balance					1,167	[1]					566	[1]	1,167	[1]	566	[1]	900
Charge-offs													(495)	[1]	(492)	[1]	(386)	[1]
Recoveries													67	[1]	64	[1]	87	[1]
Net charge-offs													(428)	[1]	(428)	[1]	(299)	[1]
Provision for loan losses													522	[1]	1,029	[1]	(20)	[1]
Benefit attributable to FDIC loss-share agreements													0	[1]	0	[1]	(15)	[1]
Recoveries payable to FDIC													0	[1]	0	[1]	0	[1]
Provision for loan losses charged to operations													522	[1]	1,029	[1]	(35)	[1]
Ending balance	1,261	[1]					1,167	[1]					1,261	[1]	1,167	[1]	566	[1]
Period-End Amount Allocated to:
Individually evaluated for impairment	0	[1]					1	[1]					0	[1]	1	[1]	0	[1]
Collectively evaluated for impairment	1,261	[1]					1,166	[1]					1,261	[1]	1,166	[1]	566	[1]
Acquired with deteriorated credit quality	0	[1]					0	[1]					0	[1]	0	[1]	0	[1]
Ending balance	$ 1,261	[1]					$ 1,167	[1]					$ 1,261	[1]	$ 1,167	[1]	$ 566	[1]

[1] Includes lease financing receivables.