Securitization Activities - Amount of Financial Assets Securitized and Cash Flows Received on Retained Interests (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Transfers and Servicing of Financial Assets [Abstract]
Securitization of residential mortgages	$ 3,107	$ 3,489
Securitization of commercial mortgages	4,996	671
Securitization of other financial assets	540	172
Securitization of Financial Assets	8,643	4,332
Retained interests cash flows	$ 94	$ 93