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Equity-Based Compensation - Summary of Key Assumptions Used for Fair Value Computation (Detail) - Performance Based Awards [Member]
12 Months Ended
Dec. 31, 2017
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award Options [Line Items]  
Expected holding period 2 years 10 months 8 days
Risk–free rate of return (as a percent) 1.46%
Expected dividend yield (as a percent) 4.72%