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Equity-Based Compensation - Schedule of Stock Options Valuation Assumptions (Detail) - $ / shares
6 Months Ended 12 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Weighted average grant-date fair value of options $ 10.45 $ 13.67
Risk-free interest rate 2.40% 2.20%
Expected volatility 38.00% 37.00%
Expected life (in years) 5 years 5 years 1 month 6 days