Unresolved Claims by Claimant (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2008 number	Dec. 31, 2013 GSE number	Dec. 31, 2012 GSE number	Dec. 31, 2013 Private Label number	Dec. 31, 2012 Private Label number
Loss Contingencies Dollars
Balance, beginning of period		$ 48	$ 47	$ 19	$ 19
New demands		259	333	4	7
Loan paydowns/payoffs		3	7	(1)
Resolved claims		(263)	(325)	(17)	(7)
Balance, end of period		$ 41	$ 48	$ 5	$ 19
Loss Contingencies Units
Balance, beginning of period		294,000,000	328,000,000	124,000,000	109,000,000
New demands	2	1,962,000,000	2,519,000,000	237,000,000	230,000,000
Loan paydowns/payoffs		(20,000,000)	(42,000,000)	(6,000,000)	(2,000,000)
Resolved claims		(1,972,000,000)	(2,511,000,000)	(322,000,000)	(213,000,000)
Balance, end of period		264,000,000	294,000,000	33,000,000	124,000,000