Related Party Transactions - Additional Information (Detail)		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 01, 2018 shares	Oct. 31, 2018 shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2018 USD ($) Investment	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Investment shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Related Party Transaction [Line Items]
Total components due to affiliates			$ 248,261,000	$ 248,261,000		$ 248,261,000		$ 133,071,000
Management fee				11,823,000	$ 3,712,000	$ 28,073,000	$ 3,712,000
Stock repurchased | shares						2,853,000
Stock repurchased, value						$ 30,603,000	187,000
Recognized liabilities for Performance Participation expense				12,447,000	$ 5,711,000	$ 29,796,000	$ 10,952,000	17,000,000
Class I Shares [Member]
Related Party Transaction [Line Items]
Stock repurchased | shares						1,194,000
Adviser [Member]
Related Party Transaction [Line Items]
Percentage of management fee on NAV per annum						1.25%
Special Limited Partner [Member]
Related Party Transaction [Line Items]
Stock issued as payment for services | shares	1,600,000
LNLS [Member]
Related Party Transaction [Line Items]
Costs paid to LNLS for title services related to investments				$ 3,100,000		$ 3,700,000
Number of Investments with Capitalized Costs | Investment				13		13
Accrued Liabilities [Member]
Related Party Transaction [Line Items]
Total components due to affiliates			0	$ 0		$ 0
Accrued Stockholder Servicing Fee [Member]
Related Party Transaction [Line Items]
Total components due to affiliates			203,199,000	203,199,000		203,199,000		102,076,000
Advanced Organization and Offering Costs [Member]
Related Party Transaction [Line Items]
Total components due to affiliates			8,693,000	8,693,000		8,693,000		10,160,000
Advanced Expenses [Member]
Related Party Transaction [Line Items]
Total components due to affiliates			729,000	729,000		729,000		472,000
Accrued Management Fee [Member]
Related Party Transaction [Line Items]
Total components due to affiliates			4,265,000	4,265,000		4,265,000		$ 1,904,000
Accrued Management Fee [Member] | Adviser [Member]
Related Party Transaction [Line Items]
Total components due to affiliates			$ 4,300,000	$ 4,300,000		$ 4,300,000
Management Fee [Member] | Adviser [Member] | Class I Shares [Member]
Related Party Transaction [Line Items]
Stock issued as payment for services | shares						2,220,262
Stock repurchased | shares			700,298
Stock repurchased, value			$ 7,600,000
Management Fee [Member] | Subsequent Event [Member] | Adviser [Member] | Class I Shares [Member]
Related Party Transaction [Line Items]
Stock issued as payment for services | shares		393,894