Capital Transactions -Additional Information (Detail)		1 Months Ended				9 Months Ended	12 Months Ended			19 Months Ended	35 Months Ended
	Mar. 07, 2018 USD ($)	Dec. 31, 2020 USD ($) shares	Jan. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2021 USD ($) class portfolioCompany $ / shares shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019	Dec. 31, 2020 USD ($) shares	Dec. 31, 2020 USD ($) offering
Investment Company, Capital Share Transactions [Line Items]
Number classes of shares | portfolioCompany							4
Authorized amount per quarter (in percent)							2.50%
Authorized amount per year (in percent)							10.00%
Repurchase of common shares pursuant to share repurchase program							$ 3,290,868	$ 9,646,917
Amount of share requested to be repurchased in excess of proceeds received from its distribution reinvestment plan								7,800,000
Payable for shares repurchased		$ 1,968,732					$ 508,770	$ 1,968,732		$ 1,968,732	$ 1,968,732
Proceeds from Public Offering
Investment Company, Capital Share Transactions [Line Items]
Shares offered	$ 1,000,000,000
Number classes of shares | class							4
Sale of stock offering, minimum requirement	$ 5,000
Shares Issued | shares							5,324,390	4,367,120
2019 Private Placement and Follow On Private Placement
Investment Company, Capital Share Transactions [Line Items]
Shares offered				$ 50,000,000	$ 50,000,000
Distribution Reinvestment Plan
Investment Company, Capital Share Transactions [Line Items]
Shares offered							$ 100,000,000
Follow On Private Placement
Investment Company, Capital Share Transactions [Line Items]
Gross Proceeds										$ 8,000,000
Shares Issued | shares										300,000
Class S Private Offering
Investment Company, Capital Share Transactions [Line Items]
Shares offered			$ 50,000,000
Gross Proceeds		$ 52,000,000
Shares Issued | shares		1,800,000
Private Placements
Investment Company, Capital Share Transactions [Line Items]
Number Of Private Offerings | offering											4
Gross Proceeds											$ 177,000,000
2019 Private Offering
Investment Company, Capital Share Transactions [Line Items]
Gross Proceeds						$ 35,000,000
Shares Issued | shares						1,300,000
Class FA
Investment Company, Capital Share Transactions [Line Items]
Repurchase of common shares pursuant to share repurchase program							$ 630,608	$ 7,037,470
Class FA | Follow On Private Placement
Investment Company, Capital Share Transactions [Line Items]
Placement agent fee on share sold percentage							3.00%		3.00%
Selling commission on share sold percentage						5.50%	5.50%		5.50%
Class FA | 2019 Private Offering
Investment Company, Capital Share Transactions [Line Items]
Shares Issued | shares								300,000
Class A
Investment Company, Capital Share Transactions [Line Items]
Repurchase of common shares pursuant to share repurchase program							$ 627,150	$ 123,038
Class A | Proceeds from Public Offering
Investment Company, Capital Share Transactions [Line Items]
Share price (usd per share) | $ / shares							$ 33.83
Class T
Investment Company, Capital Share Transactions [Line Items]
Repurchase of common shares pursuant to share repurchase program							$ 574,225	721,226
Class T | Proceeds from Public Offering
Investment Company, Capital Share Transactions [Line Items]
Share price (usd per share) | $ / shares							$ 32.20
Class D
Investment Company, Capital Share Transactions [Line Items]
Repurchase of common shares pursuant to share repurchase program							$ 198,484	32,212
Class D | Proceeds from Public Offering
Investment Company, Capital Share Transactions [Line Items]
Share price (usd per share) | $ / shares							$ 30.34
Class I
Investment Company, Capital Share Transactions [Line Items]
Repurchase of common shares pursuant to share repurchase program							$ 1,118,904	1,732,971
Class I | Proceeds from Public Offering
Investment Company, Capital Share Transactions [Line Items]
Share price (usd per share) | $ / shares							$ 31.34
Class S
Investment Company, Capital Share Transactions [Line Items]
Repurchase of common shares pursuant to share repurchase program							$ 141,497	$ 0
Class S | Class S Private Offering
Investment Company, Capital Share Transactions [Line Items]
Placement agent fee on share sold percentage							1.50%	1.50%
Selling commission on share sold percentage		2.00%					2.00%	2.00%		2.00%	2.00%