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Consolidated Financial Statements - Narrative (Details) $ in Thousands		6 Months Ended	15 Months Ended
	Dec. 31, 2020 USD ($)	Jun. 30, 2021 USD ($) loan	Jun. 30, 2021 USD ($) loan	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Unusual or Infrequent Item, or Both [Line Items]
Allowance for credit loss	$ 37,607	$ 39,493	$ 39,493	$ 43,197	$ 38,520	$ 36,800	$ 28,707
Unfounded credit commitment	808	1,808	1,808	1,702
Financing receivable	3,823,238	3,817,273	3,817,273
Net loans held-for-investment	3,785,631	$ 3,777,780	3,777,780
Cumulative Effect, Period of Adoption, Adjustment
Unusual or Infrequent Item, or Both [Line Items]
Increase in allowance for credit losses	11,100
Allowance for credit loss	10,353
Unfounded credit commitment	737			$ 0
PCD loan related reserves	6,800
Non-PCD loan related reserves	$ 4,300
COVID-19
Unusual or Infrequent Item, or Both [Line Items]
Loan modification program, payment deferral period		90 days
Loan modification program, extension for payment deferral period		90 days
Net loans held-for-investment		$ 21,500	21,500
COVID-19
Unusual or Infrequent Item, or Both [Line Items]
Financing receivable		$ 232,200	$ 232,200
Number of loans approved | loan		2,300	2,300
Net loans held-for-investment		$ 132,700	$ 132,700
Loan processing fee		9,500	9,500
Loan processing fee recognized as earnings		$ 2,800	$ 4,700
Number of loans outstanding | loan		1,453	1,453

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