Note Loans (Composition of loans held-in-portfolio-covered loans and past due status) (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Loans Held for Investment \| Covered Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged Financial Instruments, Not Separately Reported, Loans Receivable Pledged as Collateral	$ 325	$ 337

The sum of the carrying amounts, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and for which the transferees are not permitted to sell or re-pledge them to an unrelated party.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

Name:	us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedLoansReceivablePledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant