Guarantees Repurchase Requests (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Repurchase Requests [Abstract]
Principal Balance Of Unresolved Repurchase Requests	$ 47	$ 126	$ 655	$ 590
Repurchase Request Amount, Loans Sold, All Vintages	158	1,511	1,726
Repurchased or otherwise settled loans, unpaid principal balance	(28)	(1,134)	(769)
cured loans unpaid principal balance	(209)	(906)	(892)
Repurchase request amount loans resolved	$ (237)	$ (2,040)	$ (1,661)
Percent of repurchase request amount pending all vintages	6.70%	2.80%	2.50%
Percent of repurchase request amount loans sold all vintages	0.90%	1.20%	1.20%