Expected Losses to be Paid (Components of Development and Accretion Amounts of Estimated Recoveries) (Details 8) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Expected Losses [Abstract]
Inclusion of new deals with breaches of R&W during period	$ 0	$ 0
Change in recovery assumptions as the result of additional file review and recovery success	11	80
Estimated increase (decrease) in defaults that will result in additional breaches	1	(82)
Results of settlements	142	48
Accretion of discount on balance	3	5
Expected Future Recoveries for Breached Representations and Warranties Development and Accretion of Discount	$ 157	$ 51