Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Summary of RSU Grants (Detail)

v3.8.0.1
Equity-Based Compensation - Summary of RSU Grants (Detail) - Restricted Stock Units - $ / shares
9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Beginning Balance, Units 739,256 966,510 966,510
Granted, Units   14,373  
Vested, Units (247,471)    
Ending Balance, Units 491,785 980,883 739,256
Fair Value per unit   $ 13.23 $ 13.23
Fair Value per unit, Granted   13.19  
Minimum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Fair Value per unit $ 13.19    
Fair Value per unit, Vested 13.19    
Fair Value per unit 13.19 13.19 13.19
Maximum      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Fair Value per unit 13.23    
Fair Value per unit, Vested 13.23    
Fair Value per unit $ 13.23 $ 13.23 $ 13.23