Securities - Rollforward of Credit Losses Recognized (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Rollforward of Credit Losses Recognized:
Balance, beginning of period	$ 195	$ 205	$ 184	$ 243
Additions for credit losses recognized on AFS debt securities that had no previous impairment losses	0	1	11	6
Additions for credit losses recognized on AFS debt securities that had previously incurred impairment losses	1	6	1	14
Reductions for AFS debt securities matured, sold or intended to be sold	0	0	0	(51)
Balance, September 30	$ 196	$ 212	$ 196	$ 212