Loans and the Allowance for Loan Losses (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Past due and nonaccrual loans
Total Loans	$ 3,987,874	$ 3,881,018
Commercial, financial, agricultural
Past due and nonaccrual loans
Total Loans	483,283	468,963
Lease financing
Past due and nonaccrual loans
Total Loans	10,427	53
Real estate – construction
Past due and nonaccrual loans
Total Loans	212,061	161,436
Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total Loans	1,236,360	1,208,233
Real estate – commercial mortgage
Past due and nonaccrual loans
Total Loans	1,956,914	1,950,572
Installment loans to individuals
Past due and nonaccrual loans
Total Loans	89,142	91,762
Unearned income
Past due and nonaccrual loans
Total Loans	(313)
Accruing Loans
Past due and nonaccrual loans
30-89 Days Past Due	17,166	22,475
90 Days or More Past Due	10,713	4,187
Current Loans	3,915,598	3,782,025
Total Loans	3,943,477	3,808,687
Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
30-89 Days Past Due	1,113	2,067
90 Days or More Past Due	636	607
Current Loans	480,332	463,521
Total Loans	482,081	466,195
Accruing Loans | Lease financing
Past due and nonaccrual loans
30-89 Days Past Due	462	0
90 Days or More Past Due	0	0
Current Loans	9,965	53
Total Loans	10,427	53
Accruing Loans | Real estate – construction
Past due and nonaccrual loans
30-89 Days Past Due	0	664
90 Days or More Past Due	37	0
Current Loans	211,860	159,124
Total Loans	211,897	159,788
Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
30-89 Days Past Due	8,398	10,168
90 Days or More Past Due	2,382	2,206
Current Loans	1,212,214	1,179,703
Total Loans	1,222,994	1,192,077
Accruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
30-89 Days Past Due	6,924	8,870
90 Days or More Past Due	7,637	1,286
Current Loans	1,912,758	1,888,745
Total Loans	1,927,319	1,898,901
Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
30-89 Days Past Due	269	706
90 Days or More Past Due	21	88
Current Loans	88,782	90,880
Total Loans	89,072	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	(313)	(1)
Total Loans	(313)	(1)
Nonaccruing Loans
Past due and nonaccrual loans
30-89 Days Past Due	2,197	2,307
90 Days or More Past Due	22,575	47,167
Current Loans	19,625	22,857
Total Loans	44,397	72,331
Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
30-89 Days Past Due	16	138
90 Days or More Past Due	820	1,959
Current Loans	366	671
Total Loans	1,202	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	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	164	1,648
Current Loans	0	0
Total Loans	164	1,648
Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
30-89 Days Past Due	355	1,203
90 Days or More Past Due	4,604	6,041
Current Loans	8,407	8,912
Total Loans	13,366	16,156
Nonaccruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
30-89 Days Past Due	1,826	966
90 Days or More Past Due	16,928	37,439
Current Loans	10,841	13,266
Total Loans	29,595	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	59	80
Current Loans	11	8
Total Loans	70	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	$ 0	$ 0