Fair Value of Assets and Liabilities - Summary of Valuation Techniques and Significant Unobservable Inputs Used in Non-Recurring Level 3 Fair Value Measurements of Assets and Liabilities (Detail)	9 Months Ended		12 Months Ended
	Sep. 30, 2023 USD ($) $ / shares		Dec. 31, 2022 USD ($) $ / shares		Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity investments	$ 1,700,000		$ 1,700,000
Principal portion of loans serviced, fair value	15,600,000		19,500,000
Loan collateral in process of foreclosure	$ 15,923,000	[1]	$ 21,819,000	[1]	$ 16,803,000	$ 24,331,000	$ 26,974,000	$ 37,430,000
Equity Investments [Member] | Precedent Market Transactions [Member] | Equity Method Offering Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity Value | $ / shares	$ 8.73		$ 8.73
Impaired Loans [Member] | Market Approach [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans, balance percentage			0.60
Impaired Loans [Member] | Market Approach [Member] | Historical and Actual Loss Experience [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans value	0		0
Impaired Loans [Member] | Market Approach [Member] | Historical and Actual Loss Experience [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans value	0.0804		0.0655
Impaired Loans [Member] | Market Approach [Member] | Measurement Input Transfer Prices [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Principal portion of loans serviced, fair value	$ 0	[2]	$ 0	[3]
Impaired Loans [Member] | Market Approach [Member] | Measurement Input Transfer Prices [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Principal portion of loans serviced, fair value	79,500	[2]	79,500	[3]
Loan Collateral in Process of Foreclosure [Member] | Market Approach [Member] | Collateral Value [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan collateral in process of foreclosure value	2,900	[4]	2,500	[5]
Loan Collateral in Process of Foreclosure [Member] | Market Approach [Member] | Collateral Value [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan collateral in process of foreclosure value	43,200	[4]	54,100	[5]
Loan Collateral in Process of Foreclosure [Member] | Market Approach [Member] | Measurement Input Transfer Prices [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan collateral in process of foreclosure value	0	[2]	0	[3]
Loan Collateral in Process of Foreclosure [Member] | Market Approach [Member] | Measurement Input Transfer Prices [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan collateral in process of foreclosure value	79,500	[2]	79,500	[3]
Level 3 [Member] | Equity Investments [Member] | Investee Financial Analysis [Member] | Measurement Input Financial Condition and Operational Performance [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity investments	10,269,000		10,020,000
Level 3 [Member] | Impaired Loans [Member] | Precedent Market Transactions [Member] | Equity Method Offering Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Equity investments	273,000		273,000
Level 3 [Member] | Impaired Loans [Member] | Market Approach [Member] | Historical and Actual Loss Experience [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Principal portion of loans serviced, fair value	20,648,000		32,133,000
Level 3 [Member] | Loan Collateral in Process of Foreclosure [Member] | Market Approach [Member] | Measurement Input Transfer Prices [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan collateral in process of foreclosure	$ 15,923,000		$ 21,819,000

[1] Includes financed sales of this collateral to third parties that are reported separately from the loan portfolio, of $6.2 million as of September 30, 2023 and $7.5 million as of December 31, 2022.

[2] Represents amount net of liquidation costs.

[3] Represents amount net of liquidation costs.

[4] Relates to the recreation portfolio.

[5] Relates to the recreation portfolio.