Fair Value of Assets and Liabilities - Additional Information (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unpaid Principal Balance	$ 19,892,000		$ 25,861,000
Recorded Balance	17,525,000		23,440,000
Allowance for Credit Losses	1,622,000		1,098,000
Other real estate owned	2,220,000		3,644,000
Mortgage servicing rights (MSR) impairment (recovery)	614,000
Mortgage Servicing Rights
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Finite-lived intangible assets, net	661,000	$ 1,569,000	1,444,000	$ 2,101,000
Mortgage servicing rights (MSR) impairment (recovery)	328,000	$ 384,000	$ 380,000
Fair Value, Nonrecurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unpaid Principal Balance	11,279,000
Recorded Balance	9,713,300
Allowance for Credit Losses	1,565,700
Fair Value, Nonrecurring | Mortgage Servicing Rights
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Indefinite-lived contractual rights	1,275,000
Finite-lived intangible assets, net	661,000
Fair Value, Nonrecurring | Carrying Amount
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other real estate owned	2,220,000
Fair Value, Nonrecurring | Fair Value
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other real estate owned	$ 9,000