Related Party Transactions - Summary of Components of Due to Affiliates (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Total components due to affiliates	$ 532,160	$ 301,581
Accrued Stockholder Servicing Fee [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	399,100	238,496
Performance Participation Allocation [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	106,383	37,484
Accrued Management Fee [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	11,054	5,124
Advanced Organization and Offering Costs [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	6,647	8,181
Accrued Affiliate Service Provider Expenses [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	7,316	3,115
Accrued Affiliate Incentive Compensation Awards [Member]
Related Party Transaction [Line Items]
Total components due to affiliates		4,714
Other [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	$ 1,660	$ 4,467