Derivatives and Hedging Activities - Fair Value of Derivative Assets by Type (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 611	$ 646
Less: Related collateral	(127)	(23)
Total derivative assets	738	669
Interest Rate [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	215	401
Foreign Exchange [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	66	77
Commodity [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	326	163
Credit [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	0	1
Other [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 4	$ 4