Securities - Schedule of Credit Losses with OTTI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at beginning of period	$ 18	$ 61	$ 42	$ 64
Credit losses on securities with previously recognized OTTI	0	3	0	3
Securities sold/settled during the period	2	(4)	(21)	(7)
Credit recoveries through yield	0	(1)	(1)	(1)
Balance at end of period	$ 20	$ 59	$ 20	$ 59