Loans - Consumer, Excluding Credit Card Loans, Other Consumer Impaired Loans and Loan Modifications (Details) (Consumer, excluding credit card, Other Consumer, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
With an allowance	$ 557		$ 557
Without an allowance	34		35
Total impaired loans	591		592
Allowance for loan losses related to impaired loans	124		117
Unpaid principal balance of impaired loans	711		719
Average impaired loans	587	600
Troubled debt restructuring	428		442
Nonaccrual
Financing Receivable, Impaired [Line Items]
Total impaired loans	464		456
Troubled debt restructuring	$ 301		$ 306