Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Beginning Balance, Units 739,256 966,510
Granted, Units   14,373
Vested, Units   (241,627)
Ending Balance, Units 491,786 739,256
Fair Value per unit, Granted   $ 13.19
Fair Value per unit, Vested   (13.23)
Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Fair Value per unit $ 13.19 13.19
Fair Value per unit 13.19 13.19
Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Fair Value per unit 13.23 13.23
Fair Value per unit $ 13.23 $ 13.23
Vested in April 2017    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vested, Units (1,000)  
Fair Value per unit, Vested $ (13.19)  
Vested in May 2017    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vested, Units (4,843)  
Fair Value per unit, Vested $ (13.19)  
Vested in August 2017    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vested, Units (241,627)  
Fair Value per unit, Vested $ (13.23)