Loans - 90+ Day Delinquent Loans Accruing Interest and Nonperforming Loans (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,505	$ 1,263
Nonperforming Loans	$ 1,170	$ 809
Percent 90 days past due and still accruing	0.65%	0.61%
Financing Receivable, Nonaccrual, Percent Past Due	0.51%	0.39%
Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 1,500	$ 1,254
Nonperforming Loans	53	70
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	1
Nonperforming Loans	$ 558	$ 549
Financing Receivable, Nonaccrual, Percent Past Due	0.79%	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	$ 219	$ 197
Financing Receivable, Nonaccrual, Percent Past Due	0.53%	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	$ 311	$ 330
Financing Receivable, Nonaccrual, Percent Past Due	1.23%	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	$ 28	$ 22
Financing Receivable, Nonaccrual, Percent Past Due	0.77%	0.61%
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	$ 5	$ 8
Nonperforming Loans	550	175
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	5	8
Nonperforming Loans	545	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	7	62
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	5	1
Nonperforming Loans	538	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	5	7
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	0	0
Nonperforming Loans	9	15
Geographic Distribution, Domestic [Member] | Credit Card Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
90 Days Past Due and Accruing	1,421	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	79	73
Nonperforming Loans	$ 53	$ 70