Securitization Activities - Amount of Financial Assets Securitized and Cash Flows Received on Retained Interests (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Transfers and Servicing of Financial Assets [Abstract]
Securitization of residential mortgages	$ 4,254	$ 2,056	$ 9,152	$ 11,258
Securitization of commercial mortgages	1,123	3,506	1,873	8,255
Securitization of other financial assets	175	478	175	478
Securitization of Financial Assets	5,552	6,040	11,200	19,991
Cash flows on retained interests	$ 115	$ 64	$ 168	$ 142