Loans - Consumer, Excluding Credit Card Loan Portfolio, PCI Accretable Yield Activity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	$ 947,651	$ 909,182	$ 947,651	$ 909,182	$ 924,838
Consumer, excluding credit card
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	375,958	369,413	375,958	369,413	372,553
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	719		719		787
Consumer, excluding credit card | Total PCI
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	231,361		231,361		216,496
Consumer, excluding credit card | Residential real estate – PCI | Total PCI
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning balance	8,722	12,639	11,159	11,768
Accretion into interest income	(303)	(345)	(958)	(1,061)
Changes in interest rates on variable-rate loans	37	51	(231)	218
Other changes in expected cash flows	46	(1,333)	(1,468)	87
Ending balance	$ 8,502	$ 11,012	$ 8,502	$ 11,012
Accretable yield percentage	4.95%	4.54%	4.88%	4.48%
Loans	$ 25,209		$ 25,209		30,576
Consumer, excluding credit card | Residential real estate – PCI | Total PCI | In Process of Active or Suspended Foreclosure
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	$ 1,100		$ 1,100		$ 1,300