Loans and Allowance for Credit Losses (Loans, Net of Unearned Income) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 21,134,282	$ 21,789,931
Residential Mortgages [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	2,423,890	2,665,212
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,583,390	1,857,295
Commercial Real Estate - Income Producing [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	3,464,626	3,357,939
Construction and Land Development [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,228,670	1,065,057
Total Commercial And Industrial [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	12,433,706	12,844,428
Total Commercial And Industrial [Member] | Commercial Non-Real Estate [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	9,612,460	9,986,983
Total Commercial And Industrial [Member] | Commercial Real Estate - Owner Occupied | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 2,821,246	$ 2,857,445