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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Transfers and Servicing of Financial Assets [Abstract]
Securitization of residential mortgages	$ 7,717	$ 4,955	$ 15,725	$ 10,258
Securitization of commercial mortgages	6,279	5,134	14,062	8,169
Securitization of other financial assets	66	218	1,189	564
Total financial assets securitized	14,062	10,307	30,976	18,991
Retained interests cash flows	$ 130	$ 91	$ 274	$ 267