Fair Value of Financial Instruments - Reconciliations of Investments of Level 3 Inputs (Detail) - Level 3 - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value balance, beginning	$ 144,195,000	$ 82,500,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements)	22,500,000
Net change in unrealized appreciation	(3,393,662)	281,000
Fair value balance, ending	163,301,338	82,781,000
Total Senior Secured Notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value balance, beginning	48,167,603	30,700,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements)	5,474,851
Net change in unrealized appreciation	0	0
Fair value balance, ending	53,642,454	30,700,000
Equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value balance, beginning	96,027,397	51,800,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements)	17,025,149
Net change in unrealized appreciation	(3,393,662)	281,000
Fair value balance, ending	$ 109,658,884	$ 52,081,000