Investment Securities - Gains and Losses Related to Investment Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Gross realized gains from sales of AFS investment securities	$ 57	$ 64	$ 104
Gross realized losses from sales of AFS investment securities	(62)	(49)	(90)
Gross losses from OTTI	(1)	(1)	(21)
Losses reclassified (from) to other comprehensive income	0	(10)	(2)
Gains (losses) related to investment securities, net	(6)	4	(9)
Impairment associated with expected credit losses	0	(10)	(11)
Impairment associated with management's intent to sell impaired securities prior to recovery in value	0	0	(6)
Impairment associated with adverse changes in timing of expected future cash flows	(1)	(1)	(6)
Net impairment losses	$ (1)	$ (11)	$ (23)