Unresolved Claims by Claimant (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended	6 Months Ended
	Dec. 31, 2009	Jun. 30, 2012 Gse [Member] number	Jun. 30, 2012 Private Label [Member] number
Loss Contingencies [Line Items]
Balance, beginning of period		$ 47	$ 19
New demands		207	3
Loan paydowns/payoffs		(3)
Resolved claims		(172)	(4)
Balance, end of period		$ 79	$ 18
Balance, beginning of period		328,000,000	109,000,000
New demands	2	1,546,000,000	119,000,000
Loan paydowns/payoffs		(22,000,000)
Resolved claims		(1,385,000,000)	(111,000,000)
Balance, end of period		467,000,000	117,000,000