Loans and Allowance for Credit Losses, Allowance Activity by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	$ 10,821	$ 11,313	$ 10,707	$ 11,960
Provision for credit losses	503	452	1,348	643
Interest income on certain impaired loans	(39)	(43)	(78)	(86)
Loan charge-offs	(1,033)	(1,059)	(2,096)	(2,215)
Loan recoveries	380	457	748	872
Net loan charge-offs	(653)	(602)	(1,348)	(1,343)
Other	(29)	(10)	(26)	(64)
Allowance for credit losses, ending balance	10,603	11,110	10,603	11,110
Total Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	6,428	6,708	6,417	6,632
Provision for credit losses	46	89	210	258
Interest income on certain impaired loans	(14)	(14)	(25)	(25)
Loan charge-offs	(231)	(173)	(431)	(356)
Loan recoveries	66	106	121	211
Net loan charge-offs	(165)	(67)	(310)	(145)
Other	3	(5)	6	(9)
Allowance for credit losses, ending balance	6,298	6,711	6,298	6,711
Total Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning balance	4,393	4,605	4,290	5,328
Provision for credit losses	457	363	1,138	385
Interest income on certain impaired loans	(25)	(29)	(53)	(61)
Loan charge-offs	(802)	(886)	(1,665)	(1,859)
Loan recoveries	314	351	627	661
Net loan charge-offs	(488)	(535)	(1,038)	(1,198)
Other	(32)	(5)	(32)	(55)
Allowance for credit losses, ending balance	$ 4,305	$ 4,399	$ 4,305	$ 4,399