Commitments and Contingencies - Additional Information (Detail) - USD ($)	May 12, 2016	Jun. 30, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Maximum credit risk for recourse associated with loans sold under Federal National Mortgage Association Delegated Underwriting and Servicing program		$ 2,600,000,000	$ 2,500,000,000
Payment of litigation settlement expense	$ 64,000,000
Range of reasonably possible losses, minimum		0
Range of reasonably possible losses, maximum		$ 40,000,000