Fair Value Measurements - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2020	Sep. 30, 2020 USD ($) Security Loan $ / Loan	Dec. 31, 2019 USD ($) Security $ / Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of bonds owned | Security		14	39
FRB’s PPP Liquidity Facility | Fixed Cost
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, basis points on variable rate	0.35%	0.35%
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, net		$ 9,849	$ 4,084
Valuation Technique Enterprise Value | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, net		$ 5,700
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan segregated, number of pools | Loan		12
Service costs assumed, per loan | $ / Loan		6.00	6.50
Average PSA assumed rate		304.00%	187.00%
Fair Value, Measurements, Recurring | 100% PSA | Fair Value, Inputs, Level 3 | Between First Month and Month 30
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate increase, each month		0.20%
Fair Value, Measurements, Recurring | Prepayment Rate | 100% PSA | Fair Value, Inputs, Level 3 | First Month
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate		0
Fair Value, Measurements, Recurring | Prepayment Rate | 100% PSA | Fair Value, Inputs, Level 3 | Month 30
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate		6.0
Fair Value, Measurements, Recurring | Prepayment Rate | 100% PSA | Fair Value, Inputs, Level 3 | Thereafter
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment rate		6.0
Fair Value, Measurements, Recurring | Discount Rate | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate		12.0	12.5
Mortgage Servicing Rights Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of residential loan portfolio		2
Corporate bonds		$ 845	$ 935
Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of bonds owned | Security		9
Corporate bonds		$ 5,673	$ 2,650
Corporate Bonds | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of bonds owned | Security		7
Corporate bonds		$ 5,700