Loans and Allowance for Loan Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 20,026,411	$ 19,004,163
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,910,081	2,690,472
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,147,867	2,115,295
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,341,779	2,384,599
Construction and Land Development [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,548,335	1,373,421
Total Commercial And Industrial [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	11,078,349	10,440,376
Total Commercial And Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,620,601	8,297,937
Total Commercial And Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 2,457,748	$ 2,142,439