Loans and Allowance for Credit Losses Summary Of Gross Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	$ 13,886,618	$ 13,854,118
Unearned income	(15,917)	(15,516)
Loans, net of unearned income	13,870,701	13,838,602	$ 13,115,505
Real-estate commercial mortage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	5,558,108	5,462,330
Loans, net of unearned income	5,558,108	5,462,330	5,227,101
Commercial - industrial, financial, and agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	4,035,333	4,088,962
Loans, net of unearned income	4,035,333	4,088,962	3,762,631
Real-estate - home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	1,659,481	1,684,439
Loans, net of unearned income	1,659,481	1,684,439	1,701,623
Real-estate - residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	1,377,459	1,376,160
Loans, net of unearned income	1,377,459	1,376,160	1,364,788
Real-estate - construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	810,872	799,988
Loans, net of unearned income	810,872	799,988	677,806
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	263,221	268,588
Loans, net of unearned income	263,221	268,588	$ 257,301
Leasing and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	179,765	170,914
Overdrafts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, gross of unearned income	$ 2,379	$ 2,737