Variable Interest Entities and Securitization Activities (Non-Consolidated VIEs) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity
Additional VIE assets owned	$ 11,969	$ 11,318
MABS
Variable Interest Entity
VIE assets (UPB)	71,287	89,288
Maximum exposure to loss	8,631	11,871
Residential Mortgages
Variable Interest Entity
VIE assets (UPB)	6,954	15,636
Commercial Mortgages
Variable Interest Entity
VIE assets (UPB)	42,974	46,464
U.S. Agency CMO
Variable Interest Entity
VIE assets (UPB)	14,969	16,223
Other Consumer or Commercial Loans
Variable Interest Entity
VIE assets (UPB)	6,390	10,965
CDO
Variable Interest Entity
VIE assets (UPB)	10,848	9,807
Maximum exposure to loss	1,172	2,052
MTOB
Variable Interest Entity
VIE assets (UPB)	7,014	5,306
Maximum exposure to loss	4,449	3,413
OSF
Variable Interest Entity
VIE assets (UPB)	3,314	3,322
Maximum exposure to loss	1,857	1,792
Other
Variable Interest Entity
VIE assets (UPB)	19,682	31,934
Maximum exposure to loss	6,740	6,849
Assets | MABS
Variable Interest Entity
Carrying value of exposure to loss	8,234	10,657
Assets | CDO
Variable Interest Entity
Carrying value of exposure to loss	1,169	1,384
Assets | MTOB
Variable Interest Entity
Carrying value of exposure to loss	6	48
Assets | OSF
Variable Interest Entity
Carrying value of exposure to loss	1,205	1,202
Assets | Other
Variable Interest Entity
Carrying value of exposure to loss	4,732	4,914
Debt and Equity Interests
Variable Interest Entity
Maximum exposure to loss	8,234	10,657
Debt and Equity Interests | MABS
Variable Interest Entity
Maximum exposure to loss	8,234	10,657
Carrying value of exposure to loss	8,234	10,657
Debt and Equity Interests | Residential Mortgages
Variable Interest Entity
Maximum exposure to loss	745	1,272
Debt and Equity Interests | Commercial Mortgages
Variable Interest Entity
Maximum exposure to loss	1,237	2,331
Debt and Equity Interests | U.S. Agency CMO
Variable Interest Entity
Maximum exposure to loss	3,443	3,439
Debt and Equity Interests | Other Consumer or Commercial Loans
Variable Interest Entity
Maximum exposure to loss	2,809	3,615
Debt and Equity Interests | CDO
Variable Interest Entity
Maximum exposure to loss	1,169	1,384
Carrying value of exposure to loss	1,169	1,384
Debt and Equity Interests | MTOB
Variable Interest Entity
Maximum exposure to loss	0	80
Carrying value of exposure to loss	0	43
Debt and Equity Interests | OSF
Variable Interest Entity
Maximum exposure to loss	1,622	1,628
Carrying value of exposure to loss	1,205	1,202
Debt and Equity Interests | Other
Variable Interest Entity
Maximum exposure to loss	4,645	4,730
Carrying value of exposure to loss	4,645	4,730
Derivative and Other Contracts | MABS
Variable Interest Entity
Maximum exposure to loss	0	0
Carrying value of exposure to loss	0	0
Derivative and Other Contracts | CDO
Variable Interest Entity
Maximum exposure to loss	0	0
Carrying value of exposure to loss	0	0
Derivative and Other Contracts | MTOB
Variable Interest Entity
Maximum exposure to loss	4,449	3,333
Carrying value of exposure to loss	6	5
Derivative and Other Contracts | OSF
Variable Interest Entity
Maximum exposure to loss	0	0
Carrying value of exposure to loss	0	0
Derivative and Other Contracts | Other
Variable Interest Entity
Maximum exposure to loss	1,768	1,686
Carrying value of exposure to loss	87	184
Liabilities | MABS
Variable Interest Entity
Carrying value of exposure to loss	0
Liabilities | CDO
Variable Interest Entity
Carrying value of exposure to loss	0
Liabilities | MTOB
Variable Interest Entity
Carrying value of exposure to loss	0
Liabilities | OSF
Variable Interest Entity
Carrying value of exposure to loss	0
Liabilities | Other
Variable Interest Entity
Carrying value of exposure to loss	185
Derivative and Other Contracts, Liabilities | MABS
Variable Interest Entity
Carrying value of exposure to loss	0
Derivative and Other Contracts, Liabilities | CDO
Variable Interest Entity
Carrying value of exposure to loss	0
Derivative and Other Contracts, Liabilities | MTOB
Variable Interest Entity
Carrying value of exposure to loss	0
Derivative and Other Contracts, Liabilities | OSF
Variable Interest Entity
Carrying value of exposure to loss	0
Derivative and Other Contracts, Liabilities | Other
Variable Interest Entity
Carrying value of exposure to loss	185
Commitments, Guarantees and Other | MABS
Variable Interest Entity
Maximum exposure to loss	397	1,214
Commitments, Guarantees and Other | CDO
Variable Interest Entity
Maximum exposure to loss	3	668
Commitments, Guarantees and Other | MTOB
Variable Interest Entity
Maximum exposure to loss	0	0
Commitments, Guarantees and Other | OSF
Variable Interest Entity
Maximum exposure to loss	235	164
Commitments, Guarantees and Other | Other
Variable Interest Entity
Maximum exposure to loss	$ 327	$ 433