Loans and the Allowance for Loan Losses (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	$ 3,957,577		$ 3,881,019
Loans and Leases Receivable, Net of Deferred Income	3,957,530		3,881,018
Commercial, financial, agricultural
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	447,826		468,963
Loans and Leases Receivable, Net of Deferred Income	447,826		468,963
Lease financing
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	1,814		53
Real estate – construction
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	176,577		161,436
Loans and Leases Receivable, Net of Deferred Income	176,577		161,436
Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	1,221,288		1,208,233
Loans and Leases Receivable, Net of Deferred Income	1,221,288		1,208,233
Real estate – commercial mortgage
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	2,015,319		1,950,572
Loans and Leases Receivable, Net of Deferred Income	2,015,319		1,950,572
Installment loans to individuals
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	94,753		91,762
Loans and Leases Receivable, Net of Deferred Income	96,520	[1]	91,814	[1]
Unearned income
Past due and nonaccrual loans
Loans and Leases Receivable, Gross	(47)		(1)
Accruing Loans
Past due and nonaccrual loans
30-89 Days Past Due	21,640		22,475
90 Days or More Past Due	8,672		4,187
Current Loans	3,862,652		3,782,025
Total Loans, Accruing	3,892,964		3,808,687
Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
30-89 Days Past Due	630		2,067
90 Days or More Past Due	972		607
Current Loans	443,663		463,521
Total Loans, Accruing	445,265		466,195
Accruing Loans | Lease financing
Past due and nonaccrual loans
30-89 Days Past Due	0		0
90 Days or More Past Due	0		0
Current Loans	1,814		53
Total Loans, Accruing	1,814		53
Accruing Loans | Real estate – construction
Past due and nonaccrual loans
30-89 Days Past Due	713		664
90 Days or More Past Due	11		0
Current Loans	174,205		159,124
Total Loans, Accruing	174,929		159,788
Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
30-89 Days Past Due	9,437		10,168
90 Days or More Past Due	5,047		2,206
Current Loans	1,193,582		1,179,703
Total Loans, Accruing	1,208,066		1,192,077
Accruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
30-89 Days Past Due	10,581		8,870
90 Days or More Past Due	2,603		1,286
Current Loans	1,955,117		1,888,745
Total Loans, Accruing	1,968,301		1,898,901
Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
30-89 Days Past Due	279		706
90 Days or More Past Due	39		88
Current Loans	94,318		90,880
Total Loans, Accruing	94,636		91,674
Accruing Loans | Unearned income
Past due and nonaccrual loans
30-89 Days Past Due	0		0
90 Days or More Past Due	0		0
Current Loans	(47)		(1)
Total Loans, Accruing	(47)		(1)
Nonaccruing Loans
Past due and nonaccrual loans
30-89 Days Past Due	2,258		2,307
90 Days or More Past Due	45,331		47,167
Current Loans	16,977		22,857
Total Loans, Nonaccuring	64,566		72,331
Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
30-89 Days Past Due	137		138
90 Days or More Past Due	1,139		1,959
Current Loans	1,285		671
Total Loans, Nonaccuring	2,561		2,768
Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
30-89 Days Past Due	0		0
90 Days or More Past Due	0		0
Current Loans	0		0
Total Loans, Nonaccuring	0		0
Nonaccruing Loans | Real estate – construction
Past due and nonaccrual loans
30-89 Days Past Due	0		0
90 Days or More Past Due	1,648		1,648
Current Loans	0		0
Total Loans, Nonaccuring	1,648		1,648
Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
30-89 Days Past Due	336		1,203
90 Days or More Past Due	7,306		6,041
Current Loans	5,580		8,912
Total Loans, Nonaccuring	13,222		16,156
Nonaccruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
30-89 Days Past Due	1,785		966
90 Days or More Past Due	35,136		37,439
Current Loans	10,097		13,266
Total Loans, Nonaccuring	47,018		51,671
Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
30-89 Days Past Due	0		0
90 Days or More Past Due	102		80
Current Loans	15		8
Total Loans, Nonaccuring	117		88
Nonaccruing Loans | Unearned income
Past due and nonaccrual loans
30-89 Days Past Due	0		0
90 Days or More Past Due	0		0
Current Loans	0		0
Total Loans, Nonaccuring	$ 0		$ 0

[1] Includes lease financing receivables.