Borrowings and Borrowing Capacity - Summary of Information Concerning FHLB Advances (Details) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Federal home loan bank advances, amount outstanding at end of period	$ 435,000,000	$ 430,000,000
Weighted average interest rate at end of period	0.15%	1.58%
Average amount outstanding during the period	$ 430,250,000	$ 369,548,000
Weighted average interest rate during the period	0.61%	2.32%
Highest month end balance during the period	$ 850,000,000	$ 530,000,000

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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Period Type:	instant

- References

No definition available.

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- Definition

The calculated average balance outstanding for the year for all Federal Home Loan Bank advances as of the Balance Sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

The calculated weighted average interest rate for Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

+ References

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- Definition

The calculated weighted average interest rate for Federal Home Loan Bank advances for the period ended as of the Balance Sheet date.

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- Definition

The maximum balance outstanding at any month end during the period as of the Balance Sheet date.

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