Note Loans (Loans in non-performing status and accruing loans past-due 90 days or more by loan class) (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2018		Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held-in-portfolio, net of unearned income	$ 24,087,937	[1],[2]	$ 24,292,794	[3],[4]
Mortgage loans related to buy-back option program	24,224,793		24,423,427
Buy back option program
Financing Receivable, Recorded Investment, Past Due [Line Items]
Mortgage loans related to buy-back option program	535,000		840,000
ASC Subtopic 310-30
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held-in-portfolio, net of unearned income	209,000		215,000
Reverse Mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past-due 90 days or more	57,000		58,000
Residential mortgage loans insured By FHA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing loans past-due 90 days or more	$ 194,000		$ 178,000

[1] Includes $7.1 billion pledged to secure credit facilities and public funds that the secured parties are not permitted to sell or repledge the collateral, of which $4.6 billion were pledged at the Federal Home Loan Bank ("FHLB") as collateral for borrowings, $2.1 billion at the Federal Reserve Bank ("FRB") for discount window borrowings and $0.4 billion serve as collateral for public funds.

[2] Non-covered loans held-in-portfolio are net of $137 million in unearned income and exclude $78 million in loans held-for-sale.

[3] Includes $7.1 billion pledged to secure credit facilities and public funds that the secured parties are not permitted to sell or repledge the collateral, of which $4.6 billion were pledged at the FHLB as collateral for borrowings, $2.0 billion at the FRB for discount window borrowings and $0.5 billion serve as collateral for public funds.

[4] Non-covered loans held-in-portfolio are net of $131 million in unearned income and exclude $132 million in loans held-for-sale.