Loans - Loans HIP in past due status, non-performing status and accruing loans past-due 90 days or more by loan class (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned Income	$ 404,645	$ 355,908
Loans held-for-sale, at fair value	5,509	4,301
Loans held in portfolio	36,194,967	35,064,971
Non-accrual with no allowance	137,309	125,958
Federal Home Loan Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line Of Credit Facility Current Borrowing Capacity	4,000,000	3,500,000
FRB Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line Of Credit Facility Current Borrowing Capacity	5,800,000	4,400,000
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	34,906,455	33,716,900
Reverse Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	32,000	38,000
Residential mortgage loans insured By FHA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual with no allowance	70,000	106,000
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	7,993,348	7,695,917
Non-accrual with no allowance	68,454	84,797
Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	7,231,577	6,836,380
Guarantees from FHA or VA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans past-due 90 days or more	202,200	241,600
Loans held in portfolio	2,500,000	2,200,000
Asset pledged as collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	14,700,000	14,200,000
Asset pledged as collateral | Federal Home Loan Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	7,300,000	7,000,000
Asset pledged as collateral | FRB Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio	$ 7,400,000	$ 7,200,000