Allowance for Credit Losses (Non-PCI Impaired Loans and Leases) (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [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-PCD Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			133,358,000
With no recorded allowance			52,241,000
Loans and leases individually evaluated for impairment			185,599,000
Unpaid principal balance			200,599,000
Related allowance recorded			12,915,000
Average balance	$ 183,713,000	$ 163,161,000
Interest income recognized	1,373,000	4,013,000
Non-PCD Loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			52,516,000
With no recorded allowance			36,377,000
Loans and leases individually evaluated for impairment			88,893,000
Unpaid principal balance			95,927,000
Related allowance recorded			5,634,000
Average balance	91,050,000	78,011,000
Interest income recognized	705,000	2,072,000
Non-PCD Loans | Noncommercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			80,842,000
With no recorded allowance			15,864,000
Loans and leases individually evaluated for impairment			96,706,000
Unpaid principal balance			104,672,000
Related allowance recorded			7,281,000
Average balance	92,663,000	85,150,000
Interest income recognized	668,000	1,941,000
Construction and land development | Non-PCD Loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			1,851,000
With no recorded allowance			2,804,000
Loans and leases individually evaluated for impairment			4,655,000
Unpaid principal balance			5,109,000
Related allowance recorded			463,000
Average balance	6,130,000	3,460,000
Interest income recognized	6,000	40,000
Construction and land development | Non-PCD Loans | Noncommercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			2,470,000
With no recorded allowance			1,412,000
Loans and leases individually evaluated for impairment			3,882,000
Unpaid principal balance			4,150,000
Related allowance recorded			174,000
Average balance	3,124,000	3,473,000
Interest income recognized	25,000	93,000
Mortgage | Non-PCD Loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			42,394,000
With no recorded allowance			27,755,000
Loans and leases individually evaluated for impairment			70,149,000
Unpaid principal balance			74,804,000
Related allowance recorded			3,650,000
Average balance	70,351,000	61,962,000
Interest income recognized	551,000	1,653,000
Mortgage | Non-PCD Loans | Noncommercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			48,796,000
With no recorded allowance			11,646,000
Loans and leases individually evaluated for impairment			60,442,000
Unpaid principal balance			64,741,000
Related allowance recorded			3,278,000
Average balance	56,029,000	49,048,000
Interest income recognized	346,000	988,000
Revolving mortgage | Non-PCD Loans | Noncommercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			26,104,000
With no recorded allowance			2,765,000
Loans and leases individually evaluated for impairment			28,869,000
Unpaid principal balance			31,960,000
Related allowance recorded			2,722,000
Average balance	30,067,000	29,477,000
Interest income recognized	260,000	763,000
Consumer | Non-PCD Loans | Noncommercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			3,472,000
With no recorded allowance			41,000
Loans and leases individually evaluated for impairment			3,513,000
Unpaid principal balance			3,821,000
Related allowance recorded			1,107,000
Average balance	3,443,000	3,152,000
Interest income recognized	37,000	97,000
Other | Non-PCD Loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			406,000
With no recorded allowance			233,000
Loans and leases individually evaluated for impairment			639,000
Unpaid principal balance			661,000
Related allowance recorded			103,000
Average balance	298,000	314,000
Interest income recognized	2,000	6,000
Other commercial real estate | Non-PCD Loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			318,000
With no recorded allowance			950,000
Loans and leases individually evaluated for impairment			1,268,000
Unpaid principal balance			1,360,000
Related allowance recorded			39,000
Average balance	1,186,000	797,000
Interest income recognized	6,000	20,000
Commercial and industrial and leases | Non-PCD Loans | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
With a recorded allowance			7,547,000
With no recorded allowance			4,635,000
Loans and leases individually evaluated for impairment			12,182,000
Unpaid principal balance			13,993,000
Related allowance recorded			$ 1,379,000
Average balance	13,085,000	11,478,000
Interest income recognized	$ 140,000	$ 353,000