Unresolved Claims by Claimant (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014 number	Jun. 30, 2013 number
GSE
Loss Contingencies Dollars
Balance, beginning of period	$ 41	$ 48
New demands	59	129
Loan paydowns/payoffs	(2)	(2)
Resolved claims	(90)	(128)
Balance, end of period	8	47
Loss Contingencies Units
Balance, beginning of period	264,000,000	294,000,000
New demands	464,000,000	954,000,000
Loan paydowns/payoffs	(24,000,000)	(7,000,000)
Resolved claims	(656,000,000)	(907,000,000)
Balance, end of period	48,000,000	334,000,000
Private Label
Loss Contingencies Dollars
Balance, beginning of period	5	19
New demands		2
Loan paydowns/payoffs	(1)	(1)
Resolved claims	(3)	(14)
Balance, end of period	$ 1	$ 6
Loss Contingencies Units
Balance, beginning of period	33,000,000	124,000,000
New demands	10,000,000	153,000,000
Loan paydowns/payoffs	(2,000,000)	(7,000,000)
Resolved claims	(34,000,000)	(233,000,000)
Balance, end of period	7,000,000	37,000,000