- Assets and Liabilities with Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Cash and cash equivalents	$ 5,753	$ 4,807	$ 6,036	$ 6,338
Securities borrowed or purchased under resale agreements	19,747	31,072
Trading account assets	8,942	3,734
Other assets	8,496	6,537
Securities loaned or sold under repurchase agreements	24,616	29,141
Commercial paper and other short-term borrowings	2,360	3,425
Other liabilities	2,520	2,251
MUSA and Various other Non-Bank Subsidiaries | Affiliated Entity
Related Party Transaction [Line Items]
Cash and cash equivalents	102	117
Securities borrowed or purchased under resale agreements	2,765	5,620
Trading account assets	0	0
Other assets	161	131
Deposits	623	177
Securities loaned or sold under repurchase agreements	385	767
Commercial paper and other short-term borrowings	1,372	2,423
Long-term debt	6,042	5,391
Other liabilities	$ 63	$ 31