Variable Interest Entities and Securitization Activities - Fair Value of Transfers of Assets with Continuing Involvement (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity
Derivative assets	$ 37,850	$ 32,001
Derivative liabilities	44,938	28,434
SPE
Variable Interest Entity
Retained interests	732	2,508
Interests purchased in the secondary market	356	406
Derivative assets	400	339
Derivative liabilities	436	145
SPE | Investment grade
Variable Interest Entity
Retained interests	663	2,405
Interests purchased in the secondary market	212	280
SPE | Non-investment grade
Variable Interest Entity
Retained interests	69	103
Interests purchased in the secondary market	144	126
SPE | Level 2
Variable Interest Entity
Retained interests	669	2,407
Interests purchased in the secondary market	258	346
Derivative assets	388	337
Derivative liabilities	435	144
SPE | Level 2 | Investment grade
Variable Interest Entity
Retained interests	663	2,401
Interests purchased in the secondary market	196	278
SPE | Level 2 | Non-investment grade
Variable Interest Entity
Retained interests	6	6
Interests purchased in the secondary market	62	68
SPE | Level 3
Variable Interest Entity
Retained interests	63	101
Interests purchased in the secondary market	98	60
Derivative assets	12	2
Derivative liabilities	1	1
SPE | Level 3 | Investment grade
Variable Interest Entity
Retained interests	0	4
Interests purchased in the secondary market	16	2
SPE | Level 3 | Non-investment grade
Variable Interest Entity
Retained interests	63	97
Interests purchased in the secondary market	$ 82	$ 58