Capital Transactions -Additional Information (Detail) - USD ($)		1 Months Ended		11 Months Ended	12 Months Ended
	Mar. 07, 2018	Jan. 31, 2020	Apr. 30, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Investment Company, Capital Share Transactions [Line Items]
Amount of share requested to be repurchased in excess of proceeds received from its distribution reinvestment plan					$ 7,800,000	$ 300,000
Shares Issued, Including Reinvestments				3,854,515	4,444,642	2,524,449
Average Net Proceeds per Share				$ 25.17	$ 27.95	$ 26.93
Distributions reinvested, proceeds to company				$ 99,836	$ 2,109,793	$ 799,107
Net Proceeds to Company					124,209,924	$ 67,991,333
2019 Private Placement and Follow On Private Placement [Member]
Investment Company, Capital Share Transactions [Line Items]
Shares offered			$ 50,000,000.0
Proceeds from Offerings
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)				3,850,671		2,494,425
Shares offered	$ 1,000,000,000.0
Sale of stock offering, minimum requirement	$ 5,000
Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Shares offered					100,000,000.0
Distributions reinvested, proceeds to company				$ 99,836	$ 2,109,793	$ 799,107
Stock Issued During Period, Shares, Dividend Reinvestment Plan				3,844	77,522	30,024
2019 Private Offering, Follow On Private Offering and Public Offering [Member]
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)					4,367,120	2,494,425
Gross Proceeds					$ 125,275,212	$ 68,426,826
Sales Load(2)(3)					(3,175,081)	(1,234,600)
Net Proceeds to Company					$ 122,100,131	$ 67,192,226
Class S Private Offering
Investment Company, Capital Share Transactions [Line Items]
Shares offered		$ 50,000,000.0
Class FA
Investment Company, Capital Share Transactions [Line Items]
Shares Issued, Including Reinvestments				3,258,260	569,642	1,008,488
Average Net Proceeds per Share				$ 25.00	$ 27.53	$ 27.35
Net Proceeds to Company				$ 81,456,500	$ 15,685,040	$ 27,586,447
Class FA | 2019 Private Placement and Follow On Private Placement [Member]
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)					569,642	1,008,488
Gross Proceeds					$ 15,853,000	$ 27,628,371
Net Proceeds to Company					$ 15,685,040	27,586,447
Class FA | 2019 Private Offering [Member]
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)					300,000
Number of shares offered in 2019 Private Offering			50,000,000.0
Class FA | Follow On Private Placement [Member]
Investment Company, Capital Share Transactions [Line Items]
Sales Load(2)(3)					$ (167,960)	(41,924)
Placement Agent Fee on Share Sold Percentage					3.00%
Class FA | Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Distributions reinvested, proceeds to company				$ 0	$ 0	$ 0
Stock Issued During Period, Shares, Dividend Reinvestment Plan				0	0	0
Class A
Investment Company, Capital Share Transactions [Line Items]
Shares Issued, Including Reinvestments				192,388	369,816	477,054
Average Net Proceeds per Share				$ 26.33	$ 27.29	$ 26.59
Net Proceeds to Company				$ 5,064,779	$ 10,091,122	$ 12,682,767
Class A | Proceeds from Offerings
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)				190,046	334,440	463,565
Gross Proceeds				$ 5,435,093	$ 9,808,964	$ 13,294,279
Sales Load(2)(3)				(430,953)	$ (679,465)	(970,592)
Share price (usd per share)					$ 30.99
Net Proceeds to Company				5,004,140	$ 9,129,499	12,323,687
Class A | Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Distributions reinvested, proceeds to company				$ 60,639	$ 961,623	$ 359,080
Stock Issued During Period, Shares, Dividend Reinvestment Plan				2,342	35,376	13,489
Class T
Investment Company, Capital Share Transactions [Line Items]
Shares Issued, Including Reinvestments				31,452	481,784	167,210
Average Net Proceeds per Share				$ 26.09	$ 27.14	$ 26.78
Net Proceeds to Company				$ 820,613	$ 13,075,429	$ 4,478,330
Class T | Proceeds from Offerings
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)				31,432	473,344	166,277
Gross Proceeds				$ 861,000	$ 13,486,208	$ 4,675,452
Sales Load(2)(3)				(40,897)	$ (640,595)	(222,084)
Share price (usd per share)					$ 29.70
Net Proceeds to Company				820,103	$ 12,845,613	4,453,368
Class T | Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Distributions reinvested, proceeds to company				$ 510	$ 229,816	$ 24,962
Stock Issued During Period, Shares, Dividend Reinvestment Plan				20	8,440	933
Class D
Investment Company, Capital Share Transactions [Line Items]
Shares Issued, Including Reinvestments				122,889	152,248	182,928
Average Net Proceeds per Share				$ 25.95	$ 27.05	$ 26.36
Net Proceeds to Company				$ 3,188,533	$ 4,118,666	$ 4,822,008
Class D | Proceeds from Offerings
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)				121,797	143,074	176,604
Gross Proceeds				$ 3,160,000	$ 3,873,660	$ 4,655,674
Sales Load(2)(3)				0	$ 0	0
Share price (usd per share)					$ 27.85
Net Proceeds to Company				3,160,000	$ 3,873,660	4,655,674
Class D | Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Distributions reinvested, proceeds to company				$ 28,533	$ 245,006	$ 166,334
Stock Issued During Period, Shares, Dividend Reinvestment Plan				1,092	9,174	6,324
Class I
Investment Company, Capital Share Transactions [Line Items]
Shares Issued, Including Reinvestments				249,526	1,100,766	688,769
Average Net Proceeds per Share				$ 26.06	$ 27.77	$ 26.75
Net Proceeds to Company				$ 6,502,654	$ 30,567,081	$ 18,421,781
Class I | Proceeds from Offerings
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)				249,136	1,076,234	679,491
Gross Proceeds				$ 6,492,500	$ 29,893,733	$ 18,173,050
Sales Load(2)(3)				0	$ 0	0
Share price (usd per share)					$ 28.65
Net Proceeds to Company				6,492,500	$ 29,893,733	18,173,050
Class I | Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Distributions reinvested, proceeds to company				$ 10,154	$ 673,348	$ 248,731
Stock Issued During Period, Shares, Dividend Reinvestment Plan				390	24,532	9,278
Common Class S- [Member]
Investment Company, Capital Share Transactions [Line Items]
Shares Issued, Including Reinvestments					1,770,386
Average Net Proceeds per Share					$ 28.62
Net Proceeds to Company					$ 50,672,586
Common Class S- [Member] | Distribution Reinvestment Plan [Member]
Investment Company, Capital Share Transactions [Line Items]
Distributions reinvested, proceeds to company					$ 0
Stock Issued During Period, Shares, Dividend Reinvestment Plan					0
Common Class S- [Member] | Class S Private Offering
Investment Company, Capital Share Transactions [Line Items]
Shares (in shares)					1,770,386
Gross Proceeds					$ 52,359,647
Sales Load(2)(3)					(1,687,061)
Net Proceeds to Company					$ 50,672,586
Number of shares offered in 2019 Private Offering		50,000,000.0
Placement Agent Fee on Share Sold Percentage					1.50%