Allowance for Credit Losses (Non-PCI Impaired Loans and Leases) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
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	41,000,000.0
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	133,358,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	52,241,000
Financing Receivable, Individually Evaluated for Impairment	185,599,000
Outstanding principal balance	200,599,000
ALLL for loans and leases individually evaluated for impairment	12,915,000
Impaired Financing Receivable, Average Recorded Investment	169,938,000	$ 153,123,000
Impaired Financing Receivable, Interest Income, Accrual Method	5,410,000	5,488,000
Non-PCI Loans | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	52,516,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	36,377,000
Financing Receivable, Individually Evaluated for Impairment	88,893,000
Outstanding principal balance	95,927,000
ALLL for loans and leases individually evaluated for impairment	5,634,000
Impaired Financing Receivable, Average Recorded Investment	81,477,000	78,597,000
Impaired Financing Receivable, Interest Income, Accrual Method	2,761,000	3,063,000
Non-PCI Loans | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	80,842,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	15,864,000
Financing Receivable, Individually Evaluated for Impairment	96,706,000
Outstanding principal balance	104,672,000
ALLL for loans and leases individually evaluated for impairment	7,281,000
Impaired Financing Receivable, Average Recorded Investment	88,461,000	74,526,000
Impaired Financing Receivable, Interest Income, Accrual Method	2,649,000	2,425,000
Non-PCI Loans | Construction and land development | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,851,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,804,000
Financing Receivable, Individually Evaluated for Impairment	4,655,000
Outstanding principal balance	5,109,000
ALLL for loans and leases individually evaluated for impairment	463,000
Impaired Financing Receivable, Average Recorded Investment	3,915,000	1,734,000
Impaired Financing Receivable, Interest Income, Accrual Method	53,000	84,000
Non-PCI Loans | Construction and land development | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,470,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,412,000
Financing Receivable, Individually Evaluated for Impairment	3,882,000
Outstanding principal balance	4,150,000
ALLL for loans and leases individually evaluated for impairment	174,000
Impaired Financing Receivable, Average Recorded Investment	3,589,000	3,677,000
Impaired Financing Receivable, Interest Income, Accrual Method	116,000	172,000
Non-PCI Loans | Mortgage | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	42,394,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	27,755,000
Financing Receivable, Individually Evaluated for Impairment	70,149,000
Outstanding principal balance	74,804,000
ALLL for loans and leases individually evaluated for impairment	3,650,000
Impaired Financing Receivable, Average Recorded Investment	64,363,000	65,943,000
Impaired Financing Receivable, Interest Income, Accrual Method	2,188,000	2,569,000
Non-PCI Loans | Mortgage | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	48,796,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	11,646,000
Financing Receivable, Individually Evaluated for Impairment	60,442,000
Outstanding principal balance	64,741,000
ALLL for loans and leases individually evaluated for impairment	3,278,000
Impaired Financing Receivable, Average Recorded Investment	52,045,000	41,368,000
Impaired Financing Receivable, Interest Income, Accrual Method	1,386,000	1,237,000
Non-PCI Loans | Other commercial real estate | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	318,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	950,000
Financing Receivable, Individually Evaluated for Impairment	1,268,000
Outstanding principal balance	1,360,000
ALLL for loans and leases individually evaluated for impairment	39,000
Impaired Financing Receivable, Average Recorded Investment	919,000	1,225,000
Impaired Financing Receivable, Interest Income, Accrual Method	27,000	43,000
Non-PCI Loans | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,547,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,635,000
Financing Receivable, Individually Evaluated for Impairment	12,182,000
Outstanding principal balance	13,993,000
ALLL for loans and leases individually evaluated for impairment	1,379,000
Impaired Financing Receivable, Average Recorded Investment	11,884,000	9,560,000
Impaired Financing Receivable, Interest Income, Accrual Method	482,000	364,000
Non-PCI Loans | Other | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	406,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	233,000
Financing Receivable, Individually Evaluated for Impairment	639,000
Outstanding principal balance	661,000
ALLL for loans and leases individually evaluated for impairment	103,000
Impaired Financing Receivable, Average Recorded Investment	396,000	135,000
Impaired Financing Receivable, Interest Income, Accrual Method	11,000	3,000
Non-PCI Loans | Revolving mortgage | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	26,104,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,765,000
Financing Receivable, Individually Evaluated for Impairment	28,869,000
Outstanding principal balance	31,960,000
ALLL for loans and leases individually evaluated for impairment	2,722,000
Impaired Financing Receivable, Average Recorded Investment	29,516,000	26,759,000
Impaired Financing Receivable, Interest Income, Accrual Method	1,009,000	900,000
Non-PCI Loans | Consumer | Noncommercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	3,472,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	41,000
Financing Receivable, Individually Evaluated for Impairment	3,513,000
Outstanding principal balance	3,821,000
ALLL for loans and leases individually evaluated for impairment	1,107,000
Impaired Financing Receivable, Average Recorded Investment	3,311,000	2,722,000
Impaired Financing Receivable, Interest Income, Accrual Method	$ 138,000	$ 116,000