Expected Loss to be Paid - Components of Development and Accretion Amounts of Estimated Recoveries (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Expected Losses [Abstract]
Estimated increase (decrease) in defaults that will result in additional (lower) breaches(1)	$ (16)	$ (4)	$ (65)	$ (15)
Inclusion or removal of deals with breaches of R&W during period	0	0	0	0
Change in recovery assumptions	0	4	0	31
Settlements and anticipated settlements	14	90	14	96
Accretion of discount on balance	1	3	3	48
Total	$ (1)	$ 93	$ (48)	$ 160