Loans and Allowance for Credit Losses - Schedule of Nonaccrual Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	$ 125,546	$ 126,987	$ 132,431
Nonaccrual With No Related Allowance	27,666
Past Due 90 Days or More and Accruing	779
Commercial
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	37,785	39,893	40,103
Nonaccrual With No Related Allowance	8,163
Past Due 90 Days or More and Accruing	70
Commercial real estate
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	51,100	51,355	58,350
Nonaccrual With No Related Allowance	19,412
Past Due 90 Days or More and Accruing	330
BBCC
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	4,048	3,869	4,530
Nonaccrual With No Related Allowance	0
Past Due 90 Days or More and Accruing	0
Residential real estate
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	24,315	23,567	20,970
Nonaccrual With No Related Allowance	0
Past Due 90 Days or More and Accruing	42
Indirect
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	2,835	2,885	3,318
Nonaccrual With No Related Allowance	0
Past Due 90 Days or More and Accruing	175
Direct
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	1,137	1,195	1,303
Nonaccrual With No Related Allowance	59
Past Due 90 Days or More and Accruing	162
Home equity
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual Amortized Cost	4,326	$ 4,223	$ 3,857
Nonaccrual With No Related Allowance	32
Past Due 90 Days or More and Accruing	$ 0

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