Fair Value of Financial Instruments - Unobservable Inputs Used in Fair Value Measurement of Investments (Detail)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	$ 163,301,338	$ 144,195,000
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	0.090
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	0.140
Total Senior Secured Notes | Discount Rate | Weighted Average | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	0.106	0.103
Total Senior Secured Notes | EBITDA Multiple | Minimum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	7.5	7.8
Total Senior Secured Notes | EBITDA Multiple | Minimum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	7.8	8.0
Total Senior Secured Notes | EBITDA Multiple | Maximum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	15.3	14.3
Total Senior Secured Notes | EBITDA Multiple | Maximum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	14.5	14.5
Total Senior Secured Notes | EBITDA Multiple | Weighted Average | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	12.2	12.3
Total Senior Secured Notes | EBITDA Multiple | Weighted Average | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Debt securities	12.1	12.2
Equity | Discount Rate | Minimum | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	0.090	0.090
Equity | Discount Rate | Maximum | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	0.140	0.140
Equity | Discount Rate | Weighted Average | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	0.001	0.103
Equity | EBITDA Multiple | Minimum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	7.5	7.8
Equity | EBITDA Multiple | Minimum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	7.8	8.0
Equity | EBITDA Multiple | Maximum | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	15.3	14.3
Equity | EBITDA Multiple | Maximum | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	14.5	14.5
Equity | EBITDA Multiple | Weighted Average | Market comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	12.2	12.3
Equity | EBITDA Multiple | Weighted Average | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input, Equity Securities	12.1	12.2
Equity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	$ 109,658,884	$ 96,027,397
Equity | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	99,799,728	89,380,662
Equity | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	9,859,156	6,646,735
Total Senior Secured Notes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	53,642,454	48,167,603
Total Senior Secured Notes | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	51,001,610	44,814,338
Total Senior Secured Notes | Transaction method
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, at fair value	$ 2,640,844	$ 3,353,265