Guarantees Repurchase Requests (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016		Mar. 31, 2015		Dec. 31, 2015	Dec. 31, 2014
Gurantees [Abstract]
Unpaid Principal Balance Of Unresolved Repurchase Requests	$ 14	[1]	$ 48	[1]	$ 17	$ 47
Unpaid Principal Balance of Repurchase Requests Received	11		20
Unpaid Principal Balance of Repurchase Requests Resolved by Repurchase	(5)		(5)
Unpaid Principal Balance of Repurchase Requests Resolved by Settlement	(9)		(14)
Unpaid Principal Balance of Repurchase Request Loans Resolved	$ (14)		$ (19)

[1] Comprised of $9 million and $45 million from the GSEs, and $5 million and $3 million from non-agency investors at March 31, 2016 and 2015, respectively.