Loans Receivable, Net - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans on non-accrual commercial real estate, multi-family, land, construction, commercial and industrial loans				$ 250,000
Impaired loan portfolio total				26,500,000
Specific reserves to loans accruing troubled debt restructurings		$ 448,000		476,000
Average balance of impaired loans	$ 31,500,000		$ 30,900,000
Financing receivables 90 days past due and still accruing		0		0
Troubled debt restructured loans		22,600,000		24,600,000
Non-accrual loan total troubled debt restructurings		9,900,000		6,600,000
Troubled debt restructured loans with accrual interest		12,800,000		$ 18,000,000.0
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in mortgage and consumer loans collateralized, foreclosure amount		3,300,000
Commercial real estate – owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in mortgage and consumer loans collateralized, foreclosure amount		12,400,000
Commercial Real Estate – Investor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in mortgage and consumer loans collateralized, foreclosure amount		10,300,000
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in mortgage and consumer loans collateralized, foreclosure amount		1,700,000
Foreclosed property held		$ 106,000