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	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unearned Income		$ 295,156	$ 265,668
Loans held-for-sale, at lower of cost or fair value		5,381	59,168
Notes Receivable Gross		32,077,769	29,240,557
Non-accrual with no allowance		177,104	236,858
Asset pledged as collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		7,400,000	6,600,000
Federal Home Loan Bank | Asset pledged as collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		4,800,000	3,200,000
FRB Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		2,600,000	1,700,000
Public Funds | Asset pledged as collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		0	1,700,000
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		30,783,152	27,749,464
Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		1,294,617	1,491,093
Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing		351,614	480,767
Notes Receivable Gross		791,055	1,028,644
Buy Back Option Program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Repurchased loans		58,000	94,000
GNMA | Bulk loan repurchase
Accounts, Notes, Loans and Financing Receivable [Line Items]
Repurchased loans	$ 687,900
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans		299,000	393,000
Notes Receivable Gross		7,397,471	7,427,196
Non-accrual with no allowance		119,098	169,856
Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		6,460,218	6,286,114
Mortgages | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		937,253	1,141,082
Mortgages | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing		337,602	471,358
Notes Receivable Gross		600,481	827,214
Mortgages | GNMA | Buy Back Option Program | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing		14,000	13,000
Reverse Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Gross		42,000	50,000
Residential mortgage loans insured By FHA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual with no allowance		$ 190,000	$ 304,000