Loans and Allowance for Credit Losses (Composition of Nonaccrual Loans and Without an Allowance for Loan Loss by Portfolio Class) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	$ 83,551	$ 139,879
Nonaccrual without allowance for loan loss	19,207	25,127
Total Commercial [Member] | Commercial Real Estate - Income Producing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	5,061	6,743
Nonaccrual without allowance for loan loss	3,932
Total Commercial [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	2,012	2,486
Nonaccrual without allowance for loan loss		1,116
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	32,775	40,573
Nonaccrual without allowance for loan loss	2,928	1,705
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	16,464	23,385
Nonaccrual without allowance for loan loss	1,583
Total Commercial And Industrial [Member] | Total Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	27,239	66,692
Nonaccrual without allowance for loan loss	10,764	22,306
Total Commercial And Industrial [Member] | Total Commercial [Member] | Commercial Non-Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	19,124	52,836
Nonaccrual without allowance for loan loss	5,275	15,268
Total Commercial And Industrial [Member] | Total Commercial [Member] | Commercial Real Estate - Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Nonaccrual	8,115	13,856
Nonaccrual without allowance for loan loss	$ 5,489	$ 7,038