Loans - 90+ Day Delinquent Loans Accruing Interest and Nonperforming Loans (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,407	$ 1,505
Nonperforming Loans	$ 1,578	$ 1,170
Percent 90 days past due and still accruing	0.62%	0.65%
Financing Receivable, Nonaccrual, Percent Past Due	0.69%	0.51%
Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,395	$ 1,500
Nonperforming Loans	48	53
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1	0
Nonperforming Loans	$ 470	$ 558
Financing Receivable, Nonaccrual, Percent Past Due	0.66%	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	$ 133	$ 219
Financing Receivable, Nonaccrual, Percent Past Due	0.31%	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	$ 307	$ 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	$ 1	$ 0
Nonperforming Loans	$ 30	$ 28
Financing Receivable, Nonaccrual, Percent Past Due	0.83%	0.77%
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 11	$ 5
Nonperforming Loans	1,050	550
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	11	5
Nonperforming Loans	1,044	545
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1	0
Nonperforming Loans	30	7
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	10	5
Nonperforming Loans	1,014	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	6	5
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	10	9
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1,303	1,421
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	92	79
Nonperforming Loans	$ 48	$ 53