Allowance for Credit Losses (Troubled Debt Restructuring) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	$ 207,130		$ 171,192
Nonaccruing	186,454	$ 168,717	121,689
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			77,536
Commercial | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			2,766
Commercial | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			61,935
Commercial | Other commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			571
Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			11,839
Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			425
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			93,656
Consumer | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			3,882
Consumer | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	50,365		57,861
Consumer | Revolving mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			28,399
Consumer | Consumer and Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			3,514
Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	158,779		128,750
Accruing | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			61,627
Accruing | Commercial | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			487
Accruing | Commercial | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			50,819
Accruing | Commercial | Other commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			571
Accruing | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			9,430
Accruing | Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			320
Accruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			67,123
Accruing | Consumer | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			1,452
Accruing | Consumer | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	33,163		41,813
Accruing | Consumer | Revolving mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			21,032
Accruing | Consumer | Consumer and Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			2,826
Nonaccruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	48,351		42,442
Nonaccruing | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			15,909
Nonaccruing | Commercial | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			2,279
Nonaccruing | Commercial | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			11,116
Nonaccruing | Commercial | Other commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			0
Nonaccruing | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			2,409
Nonaccruing | Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			105
Nonaccruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring			26,533
Nonaccruing | Consumer | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			2,430
Nonaccruing | Consumer | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	17,202		16,048
Nonaccruing | Consumer | Revolving mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			7,367
Nonaccruing | Consumer | Consumer and Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing			688
Non-PCD Loans | Commercial | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	848
Non-PCD Loans | Commercial | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	42,278
Non-PCD Loans | Commercial | Other commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	18,908
Non-PCD Loans | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	34,592
Non-PCD Loans | Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	96,626
Non-PCD Loans | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	86,929
Non-PCD Loans | Consumer | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	2,833
Non-PCD Loans | Consumer | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	29,372
Non-PCD Loans | Consumer | Revolving mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	3,190
Non-PCD Loans | Consumer | Consumer and Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	1,169
Non-PCD Loans | Accruing | Commercial | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	791
Non-PCD Loans | Accruing | Commercial | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	33,202
Non-PCD Loans | Accruing | Commercial | Other commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	17,728
Non-PCD Loans | Accruing | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	28,942
Non-PCD Loans | Accruing | Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	80,663
Non-PCD Loans | Accruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	61,315
Non-PCD Loans | Accruing | Consumer | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	1,992
Non-PCD Loans | Accruing | Consumer | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	22,232
Non-PCD Loans | Accruing | Consumer | Revolving mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	2,918
Non-PCD Loans | Accruing | Consumer | Consumer and Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	1,010
Non-PCD Loans | Nonaccruing | Commercial | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	57
Non-PCD Loans | Nonaccruing | Commercial | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	9,076
Non-PCD Loans | Nonaccruing | Commercial | Other commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	1,180
Non-PCD Loans | Nonaccruing | Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	5,650
Non-PCD Loans | Nonaccruing | Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	15,963
Non-PCD Loans | Nonaccruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	25,614
Non-PCD Loans | Nonaccruing | Consumer | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	841
Non-PCD Loans | Nonaccruing | Consumer | Mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	7,140
Non-PCD Loans | Nonaccruing | Consumer | Revolving mortgage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	272
Non-PCD Loans | Nonaccruing | Consumer | Consumer and Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Nonaccruing	159
PCD Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	23,575		$ 17,200
PCD Loans | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	16,801
PCD Loans | Nonaccruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructuring	$ 6,774