Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Grant Date Fair Value for Awards of Performance Units Inputs (Detail)

v3.10.0.1
Equity-Based Compensation - Grant Date Fair Value for Awards of Performance Units Inputs (Detail) - Performance Units - $ / shares
9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Feb. 28, 2018
Mar. 22, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share price (in dollars per share)     $ 34.44 $ 36.31
Expected volatility 34.00% 36.00%    
Risk-free interest rate 2.39% 1.46%    
Term in years 2 years 10 months 2 days 2 years 9 months 10 days