Loans and Allowance for Credit Losses on Loans - Aging of Past Due Loans by Class of Loans - Additional Information (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Aging of Past Due Loans by Class of Loans
Past due loans 30 day or greater	$ 11,585,000	$ 15,315,000
Nonaccrual loans		8,675,000
30 days or greater past due
Aging of Past Due Loans by Class of Loans
Nonaccrual loans	2,441,000	7,413,000
Less than 30 days past due
Aging of Past Due Loans by Class of Loans
Nonaccrual loans	$ 7,220,000
Less than 30 days past due nonaccrual loans held-for-investment		$ 1,262,000

Amount of financing receivable past due.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 80
-URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922355-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919253-210447

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953401-111524

Name:	us-gaap_FinancingReceivableRecordedInvestmentPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant