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Loans and Allowance for Credit Losses - Schedule of Loans by Class (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		$ 2,088,556		$ 1,843,286
Allowance for credit losses		(22,874)	$ (22,113)	(16,677)
Loans, net of allowance for credit losses	[1]	2,065,682		1,826,609
Deferred loan fees		(4,900)		983
Unrecognized purchase discounts on non-PCI loans		815		958
Financing receivable, accrued interest, net		8,800		7,700
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		498,408		246,687
Allowance for credit losses		(2,530)	(2,525)
Commercial real estate | Commercial real estate, owner-occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		304,963		308,824
Allowance for credit losses		(2,778)	(3,135)
Commercial real estate | Commercial real estate, investor-owned
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		961,208		946,317
Allowance for credit losses		(12,682)	(11,624)
Commercial real estate | Construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		73,046		61,095
Allowance for credit losses		(1,557)	(860)
Residential loans | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		104,813		116,024
Allowance for credit losses		(738)	(1,038)
Residential loans | Other residential
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		123,395		136,657
Allowance for credit losses		(998)	(1,260)
Consumer loans | Installment and other consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans, at amortized cost		22,723		$ 27,682
Allowance for credit losses		$ (291)	$ (406)
[1] Refer to Note 1, Summary of Accounting Policies, for information on the adoption of ASU 2016-13 in 2020.

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