Loans and Allowance for Loan Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 20,175,812	$ 20,026,411	$ 19,370,917
Residential Mortgages [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	2,968,271	2,910,081	2,780,359
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	2,088,923	2,147,867	2,088,378
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	2,895,468	2,341,779	2,342,192
Construction and Land Development [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,144,062	1,548,335	1,515,233
Total Commercial And Industrial [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	11,079,088	11,078,349	10,644,755
Total Commercial And Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	8,559,118	8,620,601	8,410,961
Total Commercial And Industrial [Member] | Commercial Real Estate - Owner Occupied [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 2,519,970	$ 2,457,748	$ 2,233,794