Fair Value Measurement of Assets and Liabilities - Additional Information (Details) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfer of loans to loans held for sale, net	$ 3,900,000	$ 10,200,000		$ 14,137,000	$ 823,091,000		$ 10,000,000.0
Allowance for credit loss, write-off	541,000	$ 638,000				$ 1,200,000	$ 4,200,000
Net loans	8,800,000			8,800,000		$ 8,800,000
Gain (loss) on sale of financing receivable	(1,300,000)			(1,300,000)
Collateral dependent loans amortized cost	197,600,000			197,600,000
Specific valuation allowance allocations	$ 61,100,000			61,100,000
Liquidation basis of accounting remeasurement, gain (loss) on asset			$ 0	$ 3,100,000	$ 0
Discount adjustment of the appraisals of foreclosed assets	0.00%			0.00%		0.00%
Taxi Medallion Loan Portfolio
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Collateral dependent loans amortized cost	$ 48,200,000			$ 48,200,000
Fair Value | Non-recurring fair value measurements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Reported net carrying amount of collateral dependent loans	$ 136,500,000			$ 136,500,000