STOCKHOLDERS' EQUITY - Summary of Restricted Stock, Restricted Stock Unit and Performance-based Stock Unit Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 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)	66
Forfeited (in shares)	(4)
Outstanding at end of period (in shares)	554
Unvested, at end of period (in shares)	819
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 15.56
Granted (in dollars per share) | $ / shares	34.49
Forfeited (in dollars per share) | $ / shares	15.21
Outstanding at end of period (in dollars per share) | $ / shares	19.54
Unvested at end of period (in dollars per share) | $ / shares	$ 18.71
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term, Outstanding	1 year 4 months 23 days
Weighted Average Remaining Contractual Term, Unvested	1 year 3 months 20 days
Aggregate Intrinsic Value, Outstanding at end of period | $	$ 8,873
Aggregate Intrinsic Value, Unvested at end of period | $	$ 13,796
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)	(194)
Weighted Average Grant Date Fair Value
Class A Common Stock Vested (in dollars per share) | $ / shares	$ 10.75
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)	265