Unresolved Claims by Claimant (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended	6 Months Ended
	Dec. 31, 2009	Jun. 30, 2013 GSE number	Jun. 30, 2012 GSE number	Jun. 30, 2013 Private Label number	Jun. 30, 2012 Private Label number
Loss Contingencies Dollars
Balance, beginning of period		$ 48	$ 47	$ 19	$ 19
New demands		129	207	2	3
Loan paydowns/payoffs		(2)	(3)	(1)
Resolved claims		(128)	(172)	(14)	(4)
Balance, end of period		$ 47	$ 79	$ 6	$ 18
Loss Contingencies Units
Balance, beginning of period		294,000,000	328,000,000	124,000,000	109,000,000
New demands	2	954,000,000	1,546,000,000	153,000,000	119,000,000
Loan paydowns/payoffs		(7,000,000)	(22,000,000)	(7,000,000)
Resolved claims		(907,000,000)	(1,385,000,000)	(233,000,000)	(111,000,000)
Balance, end of period		334,000,000	467,000,000	37,000,000	117,000,000