Guarantees Repurchase Requests (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016		Jun. 30, 2015		Dec. 31, 2015	Dec. 31, 2014
Gurantees [Abstract]
Unpaid Principal Balance Of Unresolved Repurchase Requests	$ 10	[1]	$ 24	[1]	$ 17	$ 47
Unpaid Principal Balance of Repurchase Requests Received	20		44
Unpaid Principal Balance of Repurchase Requests Resolved by Repurchase	(10)		(11)
Unpaid Principal Balance of Repurchase Requests Resolved by Settlement	(17)		(56)
Unpaid Principal Balance of Repurchase Request Loans Resolved	$ (27)		$ (67)
Pending Repurchase Requests from Non-Agency Investors	44.60%		5.00%
Repurchase Requests Received from Non-Agency Investors	0.00%		0.50%

[1] Comprised of $6 million and $23 million from the GSEs, and $4 million and $1 million from non-agency investors at June 30, 2016 and 2015, respectively.