Loans - 90+ Day Delinquent Loans Accruing Interest and Nonperforming Loans (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,936	$ 1,505
Nonperforming Loans	$ 1,599	$ 1,170
Percent 90 days past due and still accruing	0.79%	0.65%
Financing Receivable, Nonaccrual, Percent Past Due	0.65%	0.51%
Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,936	$ 1,500
Nonperforming Loans	42	53
Credit Card Portfolio Segment [Member] | Geographic Distribution, Domestic [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1,840	1,421
Credit Card Portfolio Segment [Member] | Geographic Distribution, Foreign [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	96	79
Nonperforming Loans	42	53
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	$ 527	$ 558
Financing Receivable, Nonaccrual, Percent Past Due	0.72%	0.79%
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 0
Nonperforming Loans	$ 223	$ 219
Financing Receivable, Nonaccrual, Percent Past Due	0.47%	0.53%
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 0
Nonperforming Loans	$ 273	$ 311
Financing Receivable, Nonaccrual, Percent Past Due	1.26%	1.23%
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 0
Nonperforming Loans	$ 31	$ 28
Financing Receivable, Nonaccrual, Percent Past Due	0.86%	0.77%
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 5
Nonperforming Loans	1,022	550
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	5
Nonperforming Loans	1,018	545
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	30	7
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	5
Nonperforming Loans	988	538
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	4	5
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	$ 8	$ 9