Loans - Consumer, Excluding Credit Card Loan Portfolio, PCI Accretable Yield Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	$ 940,440	$ 899,576	$ 940,440	$ 899,576	$ 924,838
Consumer, excluding credit card
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Loans	374,587	365,115	374,587	365,115	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	763		763		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	225,864		225,864		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	10,250	13,122	11,159	11,768
Accretion into interest income	(327)	(357)	(655)	(716)
Changes in interest rates on variable-rate loans	(548)	51	(268)	167
Other changes in expected cash flows	(653)	(177)	(1,514)	1,420
Ending balance	$ 8,722	$ 12,639	$ 8,722	$ 12,639
Accretable yield percentage	4.93%	4.55%	4.86%	4.45%
Loans	$ 26,977		$ 26,977		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	$ 1,200		$ 1,200		$ 1,300