Variable Interest Entities and Securitization Activities (Transfers of Assets with Continuing Involvement 1) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity
Derivative assets (fair value)	$ 29,173	$ 30,813
Derivative liabilities (fair value)	27,258	26,695
SPE
Variable Interest Entity
Retained interests	2,019	988
Interests purchased in the secondary market (fair value)	299	619
Derivative assets (fair value)	216	227
Derivative liabilities (fair value)	178	85
SPE \| Investment Grade
Variable Interest Entity
Retained interests	1,593	411
Interests purchased in the secondary market (fair value)	200	533
SPE \| Non-investment Grade
Variable Interest Entity
Retained interests	426	577
Interests purchased in the secondary market (fair value)	99	86
SPE \| RML
Variable Interest Entity
SPE assets (UPB)	14,376	15,555
Retained interests	21	1
Interests purchased in the secondary market (fair value)	35	16
Derivative assets (fair value)	0	1
Derivative liabilities (fair value)	0	0
SPE \| RML \| Investment Grade
Variable Interest Entity
Retained interests	17	0
Interests purchased in the secondary market (fair value)	7	0
SPE \| RML \| Non-investment Grade
Variable Interest Entity
Retained interests	4	1
Interests purchased in the secondary market (fair value)	28	16
SPE \| CML
Variable Interest Entity
SPE assets (UPB)	68,593	62,744
Retained interests	695	391
Interests purchased in the secondary market (fair value)	162	160
Derivative assets (fair value)	0	0
Derivative liabilities (fair value)	0	0
SPE \| CML \| Investment Grade
Variable Interest Entity
Retained interests	483	293
Interests purchased in the secondary market (fair value)	91	94
SPE \| CML \| Non-investment Grade
Variable Interest Entity
Retained interests	212	98
Interests purchased in the secondary market (fair value)	71	66
SPE \| U.S. Agency CMO
Variable Interest Entity
SPE assets (UPB)	16,594	11,612
Retained interests	1,573	407
Interests purchased in the secondary market (fair value)	102	439
Derivative assets (fair value)	0	0
Derivative liabilities (fair value)	0	0
SPE \| U.S. Agency CMO \| Investment Grade
Variable Interest Entity
Retained interests	1,573	407
Interests purchased in the secondary market (fair value)	102	439
SPE \| U.S. Agency CMO \| Non-investment Grade
Variable Interest Entity
Retained interests	0	0
Interests purchased in the secondary market (fair value)	0	0
SPE \| CLN and Other
Variable Interest Entity
SPE assets (UPB)	14,608	17,060
Retained interests	213	482
Interests purchased in the secondary market (fair value)	0	4
Derivative assets (fair value)	216	226
Derivative liabilities (fair value)	178	85
SPE \| CLN and Other \| Investment Grade
Variable Interest Entity
Retained interests	3	4
Interests purchased in the secondary market (fair value)	0	0
SPE \| CLN and Other \| Non-investment Grade
Variable Interest Entity
Retained interests	210	478
Interests purchased in the secondary market (fair value)	$ 0	$ 4

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