- Assets and Liabilities with Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Cash and cash equivalents	$ 8,350	$ 3,392	$ 5,753
Securities borrowed or purchased under resale agreements	22,368	20,894
Trading account assets	11,213	10,567
Other assets	9,620	9,410
Securities loaned or sold under repurchase agreements	27,285	26,437
Commercial paper and other short-term borrowings	9,263	7,066
Other liabilities	2,048	2,143
MUSA and Various other Non-Bank Subsidiaries | Affiliated Entity
Related Party Transaction [Line Items]
Cash and cash equivalents	80	119
Securities borrowed or purchased under resale agreements	1,913	3,530
Other assets	146	223
Deposits	451	362
Securities loaned or sold under repurchase agreements	148	102
Commercial paper and other short-term borrowings	1,081	969
Long-term debt	7,333	6,251
Other liabilities	$ 69	$ 61