Commitments (Unresolved Claims by Claimant) (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)
GSE
Loss Contingencies Dollars
Balance, beginning of period	$ 4	$ 6
New demands	10	20
Loan paydowns/payoffs	(1)
Resolved claims	(9)	(20)
Balance, end of period	$ 4	$ 6
Loss Contingencies Units
Balance, beginning of period	16	37
New demands	142	240
Loan paydowns/payoffs	(6)	(12)
Resolved claims	(134)	(225)
Balance, end of period	18	40
Private Label
Loss Contingencies Dollars
Balance, beginning of period		$ 1
Resolved claims		$ (1)
Loss Contingencies Units
Balance, beginning of period	2	1
New demands	3	11
Resolved claims	(4)	(9)
Balance, end of period	1	3