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STOCKHOLDERS' EQUITY - Summary of Restricted Stock, Restricted Stock Unit and Performance-based Stock Unit Activity (Detail)
$ / shares in Units, shares in Thousands, $ in Thousands
6 Months Ended
Jun. 30, 2019
USD ($)
$ / shares
shares
Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units  
Restricted Stock, Restricted Stock Units, and Performance Stock Units  
Outstanding at beginning of period (in shares) 686
Granted (in shares) 161
Forfeited (in shares) (4)
Outstanding at end of period (in shares) 627
Weighted Average Grant Date Fair Value  
Outstanding at beginning of period (in dollars per share) | $ / shares $ 15.56
Granted (in dollars per share) | $ / shares 37.02
Forfeited (in dollars per share) | $ / shares 17.75
Outstanding at end of period (in dollars per share) | $ / shares $ 18.68
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value  
Weighted Average Remaining Contractual Term, Outstanding 1 year
Aggregate Intrinsic Value, Outstanding at end of period | $ $ 10,854
Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units | Class A Common Stock  
Restricted Stock, Restricted Stock Units, and Performance Stock Units  
Class A Common Stock Vested (in shares) (216)
Weighted Average Grant Date Fair Value  
Class A Common Stock Vested (in dollars per share) | $ / shares $ 12.13
Performance-Based Stock Units  
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value  
Performance-based stock units, percentage of attainment level 100.00%
Performance-Based Stock Units | Class A Common Stock  
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value  
Number of performance-based stock units (in shares) 325
Unvested | Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units  
Restricted Stock, Restricted Stock Units, and Performance Stock Units  
Outstanding at end of period (in shares) 952
Weighted Average Grant Date Fair Value  
Outstanding at end of period (in dollars per share) | $ / shares $ 19.48
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value  
Weighted Average Remaining Contractual Term, Outstanding 1 year 1 month 6 days
Aggregate Intrinsic Value, Outstanding at end of period | $ $ 16,909