Derivatives and Hedging Activities - Fair Value of Derivative Assets by Type (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 632	$ 646
Less: Related collateral	(116)	(23)
Total derivative assets	748	669
Interest Rate [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	189	401
Foreign Exchange [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	61	77
Commodity [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	376	163
Credit [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	(1)	1
Other [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 7	$ 4