Loans Receivable, Net - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged	$ 3,851,000,000
Impaired loans on non-accrual commercial real estate, multi-family, land, construction, commercial and industrial loans	250,000
Impaired loan portfolio total	26,510,000	$ 29,797,000
Impaired Financing Receivable, Related Allowance	476,000	0
Specific reserves to loans accruing troubled debt restructurings	476,000	0	$ 0
Average balance of impaired loans	29,400,000	38,100,000	39,800,000
Interest income on non-accrual loans	372,000	419,000	639,000
Troubled debt restructuring loans	24,600,000	26,500,000
Troubled debt restructuring loans with accrual interest	18,000,000.0	22,900,000	33,300,000
Commitments to lend additional funds to borrowers	0
Loans with non-accrual of interest	17,849,000	17,415,000	20,900,000
Financing receivables 90 days past due and still accruing	0
Non-accrual loan total troubled debt restructurings	6,600,000	3,600,000	$ 8,800,000
Allowance for loan losses	0
Colonial American Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	0
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans with non-accrual of interest	7,181,000	$ 7,389,000
Recorded investment in mortgage and consumer loans collateralized, foreclosure amount	1,800,000
Foreclosed property held	$ 51,000