Guarantees Repurchase Requests (Additional Information) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014	Dec. 31, 2013
Unpaid Principal Balance of Repurchase Requests Resolved by Repurchase	$ 11		$ 11
Unpaid Principal Balance Of Unresolved Repurchase Requests	24	[1]	52	[1]	$ 47	$ 126
Unpaid Principal Balance of Repurchase Requests Received	44		113
Unpaid Principal Balance of Repurchase Requests Resolved by Settlement	56		176
Unpaid Principal Balance of Repurchase Request Loans Resolved	$ 67		$ 187
Pending Repurchase Requests from Non-Agency Investors	5.00%		5.30%
Repurchase Requests Received from Non-Agency Investors	0.50%		0.70%
US Government Sponsored Agency [Member]
Unpaid Principal Balance Of Unresolved Repurchase Requests	$ 23		$ 49
Non-Government Sponsored Agency [Member]
Unpaid Principal Balance Of Unresolved Repurchase Requests	$ 1		$ 3

[1] 1 Comprised of $23 million and $49 million from the GSEs, and $1 million and $3 million from non-agency investors at June 30, 2015 and 2014, respectively.