Equity-Based Compensation (Performance-Based Awards) - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018
Performance Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period (years)	1 year
Performance Based Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vest	0.00%
Performance Based Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vest	200.00%
Market Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period (years)	3 years
Market Based Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vest	0.00%
Market Based Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vest	150.00%