Loans and Allowance for Credit Losses, Allowance by Credit Impairment Methodology (Details) - USD ($) $ in Millions		Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Allowance for Credit Losses, Collectively evaluated		$ 10,126		$ 9,945
Allowance for Credit Losses, Individually evaluated		1,969		2,593
Total allowance for credit losses		12,109	$ 12,146	12,540	$ 12,694	$ 12,749	$ 12,512
Financing Receivable, Collectively evaluated		918,497		928,496
Financing Receivable, Individually evaluated		19,812		22,377
Loans	[1]	951,873		967,604
Commercial Portfolio Segment [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Allowance for Credit Losses, Collectively evaluated		6,032		6,392
Allowance for Credit Losses, Individually evaluated		786		1,000
Total allowance for credit losses		6,832	6,961	7,394	7,369	7,441	6,872
Financing Receivable, Collectively evaluated		495,395		500,487
Financing Receivable, Individually evaluated		4,521		5,372
Loans		500,150		506,536
Consumer Portfolio Segment [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Allowance for Credit Losses, Collectively evaluated		4,094		3,553
Allowance for Credit Losses, Individually evaluated		1,183		1,593
Total allowance for credit losses		5,277	$ 5,185	5,146	$ 5,325	$ 5,308	$ 5,640
Financing Receivable, Collectively evaluated		423,102		428,009
Financing Receivable, Individually evaluated		15,291		17,005
Loans		451,723		461,068
PCI Loans Carrying Value [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Financing Receivable, Recorded Investment, Current		13,564		16,731
PCI Loans Carrying Value [Member] | Commercial Portfolio Segment [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Financing Receivable, Recorded Investment, Current		234		677
PCI Loans Carrying Value [Member] | Consumer Portfolio Segment [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Financing Receivable, Recorded Investment, Current		13,330		16,054
Allowance for Doubtful Accounts [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses		14		2
Allowance for Doubtful Accounts [Member] | Commercial Portfolio Segment [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses		14		2
Allowance for Doubtful Accounts [Member] | Consumer Portfolio Segment [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses		$ 0		$ 0

[1] Parenthetical amounts represent assets and liabilities for which we have elected the fair value option.