Loans and Allowance for Credit Losses Summary Of Gross Loans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	$ 13,854,118,000	$ 13,124,093,000
Unearned income	(15,516,000)	(12,377,000)
Loans, net of unearned income	13,838,602,000	13,111,716,000
Loans and leases receivable, related parties	191,600,000	252,600,000
Proceeds from related party debt	12,000
Repayments of related party debt	61,000,000
Loans serviced by unrelated third party	4,800,000,000	4,900,000,000
Real estate – commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	5,462,330,000	5,197,155,000
Loans, net of unearned income	5,462,330,000	5,197,155,000
Commercial – industrial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	4,088,962,000	3,725,567,000
Loans, net of unearned income	4,088,962,000	3,725,567,000
Real estate – home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	1,684,439,000	1,736,688,000
Loans, net of unearned income	1,684,439,000	1,736,688,000
Real estate – residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	1,376,160,000	1,377,068,000
Loans, net of unearned income	1,376,160,000	1,377,068,000
Real estate – construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	799,988,000	690,601,000
Loans, net of unearned income	799,988,000	690,601,000
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	268,588,000	265,431,000
Loans, net of unearned income	268,588,000	265,431,000
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	170,914,000	127,562,000
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans before unearned income	$ 2,737,000	$ 4,021,000