Guarantees Repurchase Requests (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014	Dec. 31, 2013
Gurantees [Abstract]
Unpaid Principal Balance Of Unresolved Repurchase Requests	$ 16	[1]	$ 45	[1]	$ 47	$ 126
Unpaid Principal Balance of Repurchase Requests Received	58		139
Unpaid Principal Balance of Repurchase Requests Resolved by Repurchase	17		22
Unpaid Principal Balance of Repurchase Requests Resolved by Settlement	72		198
Unpaid Principal Balance of Repurchase Request Loans Resolved	$ 89		$ 220

[1] 1 Comprised of $15 million and $42 million from the GSEs, and $1 million and $3 million from non-agency investors at September 30, 2015 and 2014, respectively.