Loans - Consumer, Excluding Credit Card Loans, Delinquency Statistics Junior Lien Home Equity Loans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 889,907	$ 832,792	$ 747,508
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Retained	364,406	344,355	$ 294,979
Consumer, excluding credit card | Total
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 39,063	$ 45,559
Total 30 day delinquency rate	2.87%	2.77%
Consumer, excluding credit card | HELOCs | Within the revolving period
Loans and Leases Receivable Disclosure [Line Items]
Open-ended revolving period	10 years
Consumer, excluding credit card | HELOCs | Beyond the revolving period
Loans and Leases Receivable Disclosure [Line Items]
Amortization period	20 years
Consumer, excluding credit card | Junior lien | Total
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 25,437	$ 30,711
Total 30 day delinquency rate	2.32%	2.25%
Consumer, excluding credit card | Junior lien | HELOCs | Within the revolving period
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 10,304	$ 17,050
Total 30 day delinquency rate	1.27%	1.57%
Consumer, excluding credit card | Junior lien | HELOCs | Beyond the revolving period
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 13,272	$ 11,252
Total 30 day delinquency rate	3.05%	3.10%
Consumer, excluding credit card | Junior lien | HELOANs
Loans and Leases Receivable Disclosure [Line Items]
Retained	$ 1,861	$ 2,409
Total 30 day delinquency rate	2.85%	3.03%