Quarterly report pursuant to Section 13 or 15(d)

Equity - Additional Information (Detail)

v3.2.0.727
Equity - Additional Information (Detail) - 2013 Plan [Member] - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Restricted Common Stock [Member] | Employees and Directors [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares awarded     174,585  
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 $ 2.8 $ 1.5 $ 5.0 $ 2.0
Unrecognized compensation expense $ 13.7   $ 13.7  
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%