Loans and Allowance for Loan Losses - Allowances for loan losses activity (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, covered, beginning of period		$ 2,808	$ 2,954	$ 17,803
Allowance for loan losses,total loans, beginning of period		685,041	700,719	802,853
Transfer - expiration of commercial LSA, covered			(1,735)
Transfer - expiration of commercial LSA, total loans			0
Provision (credit) for loan losses, covered		857	(1,178)	(16,629)
Provision (credit) for loan losses, total loans		193,638	106,301	107,546
Loans charged off, covered		(2,228)	(2,466)	(6,708)
Loans charged off, total loans		(173,684)	(186,264)	(288,872)
Loan recoveries, covered		3	5,233	8,488
Loan recoveries, total loans		57,678	64,285	79,192
Net (charge-offs) recoveries, covered		(2,225)	2,767	1,780
Net (charge-offs) recoveries, total loans		(116,006)	(121,979)	(209,680)
Allowance for loan losses, covered, end of period		1,440	2,808	2,954
Allowance for loan losses, total loans, end of period		762,673	685,041	700,719
Commercial, Financial and Agricultural
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning of period		299,482	292,327	283,058
Transfer - expiration of commercial LSA, not covered			1,406
Provision (credit) for loan losses		116,272	17,580	36,970
Loans charged off		(25,831)	(31,627)	(47,751)
Loan recoveries		12,190	19,796	20,050
Net (charge offs) recoveries		(13,641)	(11,831)	(27,701)
Allowance for loan losses, end of period		402,113	299,482	292,327
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning of period	[1]	138,233	158,960	254,324
Transfer - expiration of commercial LSA, not covered	[1]		6
Provision (credit) for loan losses	[1]	(17,975)	(13,582)	(70,724)
Loans charged off	[1]	(3,882)	(14,970)	(43,415)
Loan recoveries	[1]	5,692	7,819	18,775
Net (charge offs) recoveries	[1]	1,810	(7,151)	(24,640)
Allowance for loan losses, end of period	[1]	122,068	138,233	158,960
Residential real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning of period	[2]	154,627	155,575	172,265
Transfer - expiration of commercial LSA, not covered	[2]		0
Provision (credit) for loan losses	[2]	(9,711)	34,962	88,685
Loans charged off	[2]	(26,630)	(48,749)	(118,422)
Loan recoveries	[2]	13,818	12,839	13,047
Net (charge offs) recoveries	[2]	(12,812)	(35,910)	(105,375)
Allowance for loan losses, end of period	[2]	132,104	154,627	155,575
Consumer loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning of period	[3]	89,891	90,903	75,403
Transfer - expiration of commercial LSA, not covered	[3]		323
Provision (credit) for loan losses	[3]	104,195	68,519	69,244
Loans charged off	[3]	(115,113)	(88,452)	(72,576)
Loan recoveries	[3]	25,975	18,598	18,832
Net (charge offs) recoveries	[3]	(89,138)	(69,854)	(53,744)
Allowance for loan losses, end of period	[3]	$ 104,948	$ 89,891	$ 90,903

[1] Includes commercial real estate – mortgage and real estate – construction loans.

[2] Includes residential real estate – mortgage, equity lines of credit and equity loans.

[3] Includes credit card, consumer direct and consumer indirect loans.