Stockholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended	12 Months Ended
	Mar. 15, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Common stock shares issued			$ 52,627,000	$ 28,998,000
Percentage limited to repurchase of shares to NAV of all classes of shares			20.00%
Shares repurchased under repurchase plan			3,979	0
Shares repurchased under repurchase plan, value			$ 100,000	$ 0
Maximum [Member]
Repurchase of shares to NAV of all classes of shares, percentage		2.00%	5.00%
Subsequent Event [Member]
Common stock shares issued	4,003,468
Common stock shares issued	$ 99,801
Common Class Y [Member]
Common stock shares issued		193,013	193,013	191,114
Common Class Y [Member] | Subsequent Event [Member]
Common stock shares issued	193,013
Common Class T [Member]
Common stock shares issued		124,581	124,581	0
Common Class T [Member] | Subsequent Event [Member]
Common stock shares issued	290,064
Common Class S [Member]
Common stock shares issued		3,773	3,773	0
Common Class S [Member] | Subsequent Event [Member]
Common stock shares issued	3,776
Common Class D [Member]
Common stock shares issued		60,934	60,934	0
Common Class D [Member] | Subsequent Event [Member]
Common stock shares issued	80,676
Common Class M [Member]
Common stock shares issued		417,992	417,992	0
Common Class M [Member] | Subsequent Event [Member]
Common stock shares issued	654,255
Common Class I [Member]
Common stock shares issued		128,526	128,526	0
Common Class I [Member] | Subsequent Event [Member]
Common stock shares issued	292,695
Common Class F [Member]
Common stock shares issued		2,471,864	2,471,864	988,801
Common Class F [Member] | Subsequent Event [Member]
Common stock shares issued	2,488,989