Investments - Industry and Geographic Dispersion of Investment Portfolio as Percentage of Total Fair Value of Investments (Detail)	Mar. 31, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Percentage of total fair value of investment	100.00%	100.00%
Commercial and Professional Services
Investment Holdings [Line Items]
Percentage of total fair value of investment	34.00%	39.20%
Hobby Goods and Supplies
Investment Holdings [Line Items]
Percentage of total fair value of investment	18.60%	21.70%
Information Services and Advisory Solutions [Member]
Investment Holdings [Line Items]
Percentage of total fair value of investment	27.60%	32.20%
Business Services [Member]
Investment Holdings [Line Items]
Percentage of total fair value of investment	13.70%	0.00%
Manufacturing [Member]
Investment Holdings [Line Items]
Percentage of total fair value of investment	6.10%	6.90%
United States
Investment Holdings [Line Items]
Percentage of total fair value of investment	100.00%	100.00%