Loans and the Allowance for Loan Losses (Details 1) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Past due and nonaccrual loans
Loans and leases receivable, gross		$ 5,414,625	$ 3,988,187
Total loans		5,413,462	3,987,874
Commercial, financial, agricultural
Past due and nonaccrual loans
Loans and leases receivable, gross		636,837	483,283
Total loans		636,837	483,283
Lease financing
Past due and nonaccrual loans
Loans and leases receivable, gross		35,978	10,427
Real estate – construction
Past due and nonaccrual loans
Loans and leases receivable, gross		357,665	212,061
Total loans		357,665	212,061
Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Loans and leases receivable, gross		1,735,323	1,236,360
Total loans		1,735,323	1,236,360
Real estate – commercial mortgage
Past due and nonaccrual loans
Loans and leases receivable, gross		2,533,729	1,956,914
Total loans		2,533,729	1,956,914
Installment loans to individuals
Past due and nonaccrual loans
Loans and leases receivable, gross		115,093	89,142
Total loans	[1]	149,908	99,256
Unearned income
Past due and nonaccrual loans
Loans and leases receivable, gross		(1,163)	(313)
Accruing Loans
Past due and nonaccrual loans
Current Loans		5,352,365	3,915,598
Total loans, accruing		5,384,428	3,943,477
Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current Loans		634,037	480,332
Total loans, accruing		636,410	482,081
Accruing Loans | Lease financing
Past due and nonaccrual loans
Current Loans		35,978	9,965
Total loans, accruing		35,978	10,427
Accruing Loans | Real estate – construction
Past due and nonaccrual loans
Current Loans		357,420	211,860
Total loans, accruing		357,665	211,897
Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current Loans		1,707,230	1,212,214
Total loans, accruing		1,722,883	1,222,994
Accruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Current Loans		2,504,192	1,912,758
Total loans, accruing		2,517,622	1,927,319
Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current Loans		114,671	88,782
Total loans, accruing		115,033	89,072
Accruing Loans | Unearned income
Past due and nonaccrual loans
Current Loans		(1,163)	(313)
Total loans, accruing		(1,163)	(313)
Nonaccruing Loans
Past due and nonaccrual loans
Current Loans		21,796	19,625
Total loans, nonaccruing		29,034	44,397
Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Current Loans		264	366
Total loans, nonaccruing		427	1,202
Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Current Loans		0	0
Total loans, nonaccruing		0	0
Nonaccruing Loans | Real estate – construction
Past due and nonaccrual loans
Current Loans		0	0
Total loans, nonaccruing		0	164
Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Current Loans		8,249	8,407
Total loans, nonaccruing		12,440	13,366
Nonaccruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Current Loans		13,276	10,841
Total loans, nonaccruing		16,107	29,595
Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Current Loans		7	11
Total loans, nonaccruing		60	70
Nonaccruing Loans | Unearned income
Past due and nonaccrual loans
Current Loans		0	0
Total loans, nonaccruing		0	0
30-89 Days Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due		15,670	17,166
30-89 Days Past Due | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Loans past due		1,296	1,113
30-89 Days Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Loans past due		0	462
30-89 Days Past Due | Accruing Loans | Real estate – construction
Past due and nonaccrual loans
Loans past due		69	0
30-89 Days Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Loans past due		9,196	8,398
30-89 Days Past Due | Accruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Loans past due		4,849	6,924
30-89 Days Past Due | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Loans past due		260	269
30-89 Days Past Due | Accruing Loans | Unearned income
Past due and nonaccrual loans
Loans past due		0	0
30-89 Days Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due		1,126	2,197
30-89 Days Past Due | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Loans past due		30	16
30-89 Days Past Due | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Loans past due		0	0
30-89 Days Past Due | Nonaccruing Loans | Real estate – construction
Past due and nonaccrual loans
Loans past due		0	0
30-89 Days Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Loans past due		528	355
30-89 Days Past Due | Nonaccruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Loans past due		568	1,826
30-89 Days Past Due | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Loans past due		0	0
30-89 Days Past Due | Nonaccruing Loans | Unearned income
Past due and nonaccrual loans
Loans past due		0	0
90 Days or More Past Due | Accruing Loans
Past due and nonaccrual loans
Loans past due		16,393	10,713
90 Days or More Past Due | Accruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Loans past due		1,077	636
90 Days or More Past Due | Accruing Loans | Lease financing
Past due and nonaccrual loans
Loans past due		0	0
90 Days or More Past Due | Accruing Loans | Real estate – construction
Past due and nonaccrual loans
Loans past due		176	37
90 Days or More Past Due | Accruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Loans past due		6,457	2,382
90 Days or More Past Due | Accruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Loans past due		8,581	7,637
90 Days or More Past Due | Accruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Loans past due		102	21
90 Days or More Past Due | Accruing Loans | Unearned income
Past due and nonaccrual loans
Loans past due		0	0
90 Days or More Past Due | Nonaccruing Loans
Past due and nonaccrual loans
Loans past due		6,112	22,575
90 Days or More Past Due | Nonaccruing Loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Loans past due		133	820
90 Days or More Past Due | Nonaccruing Loans | Lease financing
Past due and nonaccrual loans
Loans past due		0	0
90 Days or More Past Due | Nonaccruing Loans | Real estate – construction
Past due and nonaccrual loans
Loans past due		0	164
90 Days or More Past Due | Nonaccruing Loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Loans past due		3,663	4,604
90 Days or More Past Due | Nonaccruing Loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Loans past due		2,263	16,928
90 Days or More Past Due | Nonaccruing Loans | Installment loans to individuals
Past due and nonaccrual loans
Loans past due		53	59
90 Days or More Past Due | Nonaccruing Loans | Unearned income
Past due and nonaccrual loans
Loans past due		$ 0	$ 0

[1] Includes lease financing receivables.