Variable Interest Entities - Additional Information (Detail) - Credit Risk Transfer Agreements [Member]	9 Months Ended
	Sep. 30, 2024
Minimum [Member]
Mortgage Loans on Real Estate [Line Items]
Initially established percentage of unpaid principal balance of loans sold under recourse obligation losses	3.50%
Increase to maximum percentage of outstanding unpaid principal balance	4.50%
Maximum [Member]
Mortgage Loans on Real Estate [Line Items]
Initially established percentage of unpaid principal balance of loans sold under recourse obligation losses	4.00%
Increase to maximum percentage of outstanding unpaid principal balance	5.00%