Loans - 90+ Day Delinquent Loans Accruing Interest and Nonperforming Loans (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,262	$ 1,263
Nonperforming Loans	$ 1,063	$ 809
Percent 90 days past due and still accruing	0.59%	0.61%
Financing Receivable, Nonaccrual, Percent Past Due	0.50%	0.39%
Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,261	$ 1,254
Nonperforming Loans	61	70
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	1
Nonperforming Loans	$ 538	$ 549
Financing Receivable, Nonaccrual, Percent Past Due	0.76%	0.77%
Consumer Portfolio Segment [Member] | Auto
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 0
Nonperforming Loans	$ 201	$ 197
Financing Receivable, Nonaccrual, Percent Past Due	0.49%	0.52%
Consumer Portfolio Segment [Member] | Home loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 0
Nonperforming Loans	$ 310	$ 330
Financing Receivable, Nonaccrual, Percent Past Due	1.18%	1.10%
Consumer Portfolio Segment [Member] | Retail banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 0	$ 1
Nonperforming Loans	$ 27	$ 22
Financing Receivable, Nonaccrual, Percent Past Due	0.74%	0.61%
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1	$ 8
Nonperforming Loans	453	175
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1	8
Nonperforming Loans	449	168
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	7
Nonperforming Loans	8	62
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1	1
Nonperforming Loans	441	106
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	7
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	11	15
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1,196	1,181
Nonperforming Loans	0	0
Geographic Distribution, Foreign [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	65	73
Nonperforming Loans	$ 61	$ 70