Summary of Current Financial Performance Thresholds and Vesting Rates (Detail) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Threshold IRR	6.00%	6.00%	6.00%
Target IRR	8.00%	8.00%	8.00%
Maximum IRR	14.00%	14.00%	14.00%
Threshold IRR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Shares Vesting	33.30%
Targeted IRR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Shares Vesting	66.60%
Maximum IRR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Shares Vesting	100.00%