Allowance for Credit Losses (Non-PCI Impaired Loans and Leases) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-PCI Impaired Loans Collective Maximum Balance Collectively Evaluated for Impairment	$ 500,000
Impaired Financing Receivable Collectively Evaluated	41,000,000
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	169,938,000
Impaired Financing Receivable, Interest Income, Accrual Method	5,410,000
Non-PCI Loans | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	81,477,000
Impaired Financing Receivable, Interest Income, Accrual Method	2,761,000
Non-PCI Loans | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	88,461,000
Impaired Financing Receivable, Interest Income, Accrual Method	2,649,000
Non-PCI Loans | Construction and land development | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,915,000
Impaired Financing Receivable, Interest Income, Accrual Method	53,000
Non-PCI Loans | Construction and land development | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,589,000
Impaired Financing Receivable, Interest Income, Accrual Method	116,000
Non-PCI Loans | Mortgage | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	64,363,000
Impaired Financing Receivable, Interest Income, Accrual Method	2,188,000
Non-PCI Loans | Mortgage | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	52,045,000
Impaired Financing Receivable, Interest Income, Accrual Method	1,386,000
Non-PCI Loans | Other commercial real estate | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	919,000
Impaired Financing Receivable, Interest Income, Accrual Method	27,000
Non-PCI Loans | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	11,884,000
Impaired Financing Receivable, Interest Income, Accrual Method	482,000
Non-PCI Loans | Other | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	396,000
Impaired Financing Receivable, Interest Income, Accrual Method	11,000
Non-PCI Loans | Revolving mortgage | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	29,516,000
Impaired Financing Receivable, Interest Income, Accrual Method	1,009,000
Non-PCI Loans | Consumer | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Average Recorded Investment	3,311,000
Impaired Financing Receivable, Interest Income, Accrual Method	$ 138,000