Loans And Allowance For Loan Losses (Loans Outstanding By Classification) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 24,812,795	$ 23,882,382
Deferred fees and costs, net	(25,331)	(25,991)	$ (30,100)
Total loans, net of deferred fees and costs	24,787,464	23,856,391
Total commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	6,935,288	7,374,112
Total loans	6,935,288	7,374,112
Total commercial real estate | Investment properties
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	5,670,065	5,869,261
Total loans	5,670,065	5,869,261
Total commercial real estate | 1-4 family properties
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	781,619	888,553
Total loans	781,619	888,553
Total commercial real estate | Land and development
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial real estate	483,604	616,298
Total loans	483,604	616,298
Total commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial and industrial	12,023,650	11,543,806
Total loans	12,023,650	11,543,806
Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial and industrial	7,179,487	6,909,036
Total loans	7,179,487	6,909,036
Total commercial and industrial | Owner-occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total commercial and industrial	4,844,163	4,634,770
Total loans	4,844,163	4,634,770
Total consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	5,853,857	4,964,464
Total loans	5,853,857	4,964,464
Total consumer | Home equity lines
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	1,514,227	1,617,265
Total loans	1,514,227	1,617,265
Total consumer | Consumer mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	2,633,503	2,296,604
Total loans	2,633,503	2,296,604
Total consumer | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	232,676	232,413
Total loans	232,676	232,413
Total consumer | Other consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total consumer	1,473,451	818,182
Total loans	$ 1,473,451	$ 818,182