Guarantees, Pledged Assets and Collateral, and other Commitments Guarantees, Collateral Type and Contractual Maturities of Repurchase Agreements and Securities Lending Agreements (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	$ 108,109	$ 97,280
Securities Lending	8,791	8,968
Total Repurchases and Securities Lending	116,900	106,248
Securities of U.S. Treasury and federal agencies [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	49,622	38,408
Securities Lending	198	222
Securities of U.S. states and political subdivisions [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	97	159
Federal agencies [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	43,346	47,241
Securities Lending	0	2
Non-Agency Mortgage-backed Securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	1,754	1,875
Corporate debt securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	8,132	6,191
Securities Lending	483	389
Asset-backed securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	2,258	2,074
Equity securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	2,034	992
Securities Lending	8,094	8,349
Other [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	866	340
Securities Lending	16	6
Overnight/Continuous [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	96,487	86,574
Securities Lending	8,643	8,669
Total Repurchases and Securities Lending	105,130	95,243
Up to 30 days [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	3,565	3,244
Securities Lending	0	0
Total Repurchases and Securities Lending	3,565	3,244
30-90 days [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	3,938	2,153
Securities Lending	148	299
Total Repurchases and Securities Lending	4,086	2,452
Over 90 days [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	4,119	5,309
Securities Lending	0	0
Total Repurchases and Securities Lending	$ 4,119	$ 5,309