Related Party Transactions - Summary of Components of Due to Affiliates (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Total components due to affiliates	$ 317,970	$ 301,581
Accrued Stockholder Servicing Fee [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	275,432	238,496
Performance Participation Allocation [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	20,163	37,484
Advanced Organization and Offering Costs [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	7,670	8,181
Accrued Management Fee [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	6,069	5,124
Accrued Affiliate Service Provider Expenses [Member]
Related Party Transaction [Line Items]
Total components due to affiliates	2,187	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	$ 6,449	$ 4,467