- Assets and Liabilities with Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Cash and cash equivalents	$ 9,641	$ 8,350	$ 3,392
Securities borrowed or purchased under resale agreements	23,943	22,368
Trading account assets	10,377	11,213
Other assets	10,200	9,620
Commercial paper and other short-term borrowings	6,484	9,263
Other liabilities	2,837	2,048
MUSA and Various other Non-Bank Subsidiaries | Affiliated Entity
Related Party Transaction [Line Items]
Cash and cash equivalents	282	80
Securities borrowed or purchased under resale agreements	2,415	1,913
Other assets	109	146
Deposits	894	451
Securities loaned or sold under repurchase agreements	318	148
Commercial paper and other short-term borrowings	326	1,081
Long-term debt	7,345	7,333
Other liabilities	$ 98	$ 69