Schedule of Financial Instruments Owned and Pledged as Collateral (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Financial Instruments Owned and Pledged as Collateral [Line Items]
Amount of Repurchase Agreements Secured by Trading Assets		$ 928	$ 950
Repurchase Agreements [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading Securities Pledged as Collateral	[1]	968	986
Derivative [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading Securities Pledged as Collateral		471	393
Equity Trading [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Trading Securities Pledged as Collateral		$ 40	$ 40

[1] Repurchase agreements secured by collateral totaled $928 million and $950 million at December 31, 2016 and 2015, respectively.