XML 159 R142.htm IDEA: XBRL DOCUMENT v3.3.1.900
Commitments and Contingencies - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]    
Maximum credit risk for recourse associated with loans sold under Federal National Mortgage Association Delegated Underwriting and Servicing program $ 2,500,000,000 $ 2,400,000,000
Period of noncancelable operating lease in years 23 years  
Range of reasonably possible losses, minimum $ 0  
Range of reasonably possible losses, maximum $ 40,000,000