Annual report pursuant to Section 13 and 15(d)

Equity - Additional Information (Detail)

v3.3.1.900
Equity - Additional Information (Detail) - 2013 Plan [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Restricted Common Stock [Member] | Employees and Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares awarded 196,517    
Restricted common shares vesting years Vest in 2015 to 2019    
Restricted Common Stock [Member] | Certain Employees [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares awarded 390,131    
Restricted Incentive [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Equity-based compensation expense $ 11 $ 5 $ 7
Unrecognized compensation expense $ 9    
Weighted-average term in which unrecognized compensation expense is expected to be recognized 2 years    
Assumed forfeiture rate for calculation of equity-based compensation expense 5.00%