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Share-Based Compensation - Schedule of Grant Date Fair Values of Awards Using Monte Carlo Simulation Valuation Model (Detail)
6 Months Ended
Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Expected volatility 24.00% [1]
Risk-free rate 2.40%
Minimum [Member]  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Expected term 2 years
Maximum [Member]  
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Expected term 3 years
[1] Due to limited trading history of our common stock, we used the historical and implied volatilities of our peer group in addition to our historical and implied volatilities over the performance period to estimate appropriate expected volatilities.