Fair Value of Financial Instruments - Unobservable Inputs Used in Fair Value Measurement of Investments (Detail)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	$ 144,195,000	$ 82,500,000
Total Senior Secured Notes | Discount Rate | Minimum | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	0.090	0.105
Total Senior Secured Notes | Discount Rate | Maximum | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	0.140	0.135
Total Senior Secured Notes | Discount Rate | Weighted Average | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	0.103	0.114
Total Senior Secured Notes | EBITDA Multiple | Minimum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	7.8	7.9
Total Senior Secured Notes | EBITDA Multiple | Minimum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	8.0	8.0
Total Senior Secured Notes | EBITDA Multiple | Maximum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	14.3	12.2
Total Senior Secured Notes | EBITDA Multiple | Maximum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	14.5	12.0
Total Senior Secured Notes | EBITDA Multiple | Weighted Average | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	12.3	10.9
Total Senior Secured Notes | EBITDA Multiple | Weighted Average | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	12.2	10.8
Equity | Discount Rate | Minimum | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	0.090	0.105
Equity | Discount Rate | Maximum | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	0.140	0.135
Equity | Discount Rate | Weighted Average | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	0.103	0.114
Equity | EBITDA Multiple | Minimum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	7.8	7.9
Equity | EBITDA Multiple | Minimum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	8.0	8.0
Equity | EBITDA Multiple | Maximum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	14.3	12.2
Equity | EBITDA Multiple | Maximum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	14.5	12.0
Equity | EBITDA Multiple | Weighted Average | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	12.3	10.9
Equity | EBITDA Multiple | Weighted Average | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	12.2	10.8
Equity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	$ 96,027,397	$ 51,800,000
Equity | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	89,380,662	51,800,000
Equity | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	6,646,735
Total Senior Secured Notes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	48,167,603	30,700,000
Total Senior Secured Notes | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	44,814,338	$ 30,700,000
Total Senior Secured Notes | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	$ 3,353,265