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	Sep. 30, 2019	Dec. 31, 2018
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	$ 114,029	$ 97,280
Securities Lending	7,729	8,968
Total Repurchases and Securities Lending	121,758	106,248
Securities of U.S. Treasury and federal agencies [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	42,632	38,408
Securities Lending	127	222
Securities of U.S. states and political subdivisions [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	22	159
Federal agencies [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	56,007	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	1,794	1,875
Corporate debt securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	8,347	6,191
Securities Lending	273	389
Asset-backed securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	2,384	2,074
Equity securities [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	2,038	992
Securities Lending	7,322	8,349
Other [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	805	340
Securities Lending	7	6
Overnight/Continuous [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	101,997	86,574
Securities Lending	7,583	8,669
Total Repurchases and Securities Lending	109,580	95,243
Up to 30 days [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	4,042	3,244
Securities Lending	0	0
Total Repurchases and Securities Lending	4,042	3,244
30-90 days [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	3,836	2,153
Securities Lending	146	299
Total Repurchases and Securities Lending	3,982	2,452
Over 90 days [Member]
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement [Abstract]
Repurchase Agreements	4,154	5,309
Securities Lending	0	0
Total Repurchases and Securities Lending	$ 4,154	$ 5,309