Securities - Schedule of Credit Losses with OTTI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at beginning of period	$ 20	$ 59	$ 42	$ 64
Credit losses on securities with previously recognized OTTI	0	1	0	4
Securities sold/settled during the period	0	(13)	(21)	(19)
Credit recoveries through yield	0	(1)	(1)	(3)
Included as a result of loss share termination	1	0	1	0
Balance at end of period	$ 21	$ 46	$ 21	$ 46