Loans Held for Investment - Collateral Dependent Loans by Collateral Type (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	$ 21,984	$ 14,037
Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	270	288
Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	1,213	1,536
Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	2,542	2,594
Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	5,304	5,304
Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	10,182	1,455
Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	14	113
Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	2,459	2,747
Investor loans secured by real estate
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	12,724	4,049
Investor loans secured by real estate | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	2,542	2,594
Investor loans secured by real estate | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	10,182	1,455
Investor loans secured by real estate | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | CRE non-owner-occupied
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	12,284	2,792
Investor loans secured by real estate | CRE non-owner-occupied | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | CRE non-owner-occupied | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | CRE non-owner-occupied | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	2,542	2,594
Investor loans secured by real estate | CRE non-owner-occupied | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | CRE non-owner-occupied | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	9,742	198
Investor loans secured by real estate | CRE non-owner-occupied | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | CRE non-owner-occupied | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	440	1,257
Investor loans secured by real estate | SBA secured by real estate | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | SBA secured by real estate | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | SBA secured by real estate | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | SBA secured by real estate | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | SBA secured by real estate | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	440	1,257
Investor loans secured by real estate | SBA secured by real estate | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Investor loans secured by real estate | SBA secured by real estate | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	6,787	7,226
Business loans secured by real estate | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	270	288
Business loans secured by real estate | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	1,213	1,536
Business loans secured by real estate | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	5,304	5,304
Business loans secured by real estate | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	98
Business loans secured by real estate | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | SBA secured by real estate
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	727	1,143
Business loans secured by real estate | SBA secured by real estate | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	270	288
Business loans secured by real estate | SBA secured by real estate | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	457	757
Business loans secured by real estate | SBA secured by real estate | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | SBA secured by real estate | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | SBA secured by real estate | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | SBA secured by real estate | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	98
Business loans secured by real estate | SBA secured by real estate | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | CRE owner-occupied
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	6,060	6,083
Business loans secured by real estate | CRE owner-occupied | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | CRE owner-occupied | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	756	779
Business loans secured by real estate | CRE owner-occupied | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | CRE owner-occupied | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	5,304	5,304
Business loans secured by real estate | CRE owner-occupied | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | CRE owner-occupied | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Business loans secured by real estate | CRE owner-occupied | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	2,459	2,747
Commercial loans | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	2,459	2,747
Commercial loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	1,767	2,040
Commercial loans | Commercial and industrial | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Commercial and industrial | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Commercial and industrial | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Commercial and industrial | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Commercial and industrial | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Commercial and industrial | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | Commercial and industrial | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	1,767	2,040
Commercial loans | SBA non-real estate secured
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	692	707
Commercial loans | SBA non-real estate secured | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | SBA non-real estate secured | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | SBA non-real estate secured | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | SBA non-real estate secured | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | SBA non-real estate secured | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | SBA non-real estate secured | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Commercial loans | SBA non-real estate secured | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	692	707
Retail loans
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	14	15
Retail loans | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	14	15
Retail loans | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Single family residential
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	14	15
Retail loans | Single family residential | Office Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Single family residential | Industrial Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Single family residential | Retail Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Single family residential | Land Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Single family residential | Hotel Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	0	0
Retail loans | Single family residential | Residential Properties
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	14	15
Retail loans | Single family residential | Business Assets
Financing Receivable, Past Due [Line Items]
Collateral dependent loans	$ 0	$ 0