Loans, Allowance for Credit Losses - Loans, and Credit Quality - Narrative (Details)	9 Months Ended	12 Months Ended
Sep. 30, 2020 USD ($) Loan	Dec. 31, 2019 USD ($) Loan
Receivables [Abstract]
Accrued interest on loans	$ 8,000,000	$ 7,000,000
Material loans criteria for ALLL adequacy calculation	$ 250,000
Number of loans classified as troubled debt \| Loan	6	5
Troubled debt restructuring current outstanding balance	$ 1,100,000	$ 1,100,000
Pre-modification balance	$ 1,900,000	$ 1,400,000
Number of loans classified as troubled debt with subsequent default \| Loan	0

Material Loans Criteria For ACL Loans Adequacy Calculation

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- Definition

Amount, after allowance for credit loss, of accrued interest on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL120267960-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL120267845-210446

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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Amount, after troubled debt restructuring, of modified financing receivable.

+ References

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- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

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- Definition

Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524

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