Commitments, Contingent Liabilities and Guarantees - Commitments to Extend Credit or Funding (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Total loan commitments	$ 58,652	$ 52,725
When-issued and to be announced securities commitments	0	34
Commercial letters of credit	231	143
Purchase card commitments	425	293
Principal investing commitments	29	37
Tax credit investment commitments	481	466
Liabilities of certain limited partnerships and other commitments	0	2
Securities underwriting	9	0
Total loan and other commitments	59,827	53,700
Commercial and Other [Member]
Guarantor Obligations [Line Items]
Total loan commitments	40,315	34,372
Commercial Real Estate and Construction [Member]
Guarantor Obligations [Line Items]
Total loan commitments	2,774	3,034
Home Equity [Member]
Guarantor Obligations [Line Items]
Total loan commitments	9,673	9,666
Credit Cards [Member]
Guarantor Obligations [Line Items]
Total loan commitments	$ 5,890	$ 5,653