Fair Value Measurements - Summary of Valuation of Investments by Fair Value Hierarchy Levels (Detail) - USD ($)		Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		$ 366,279,562	$ 372,977,743
Senior Secured Term Loans [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value	[1]	84,349,839	88,858,707
Senior Secured Term Loan Participations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value	[1]	198,029,550	189,157,819
Senior Secured Trade Finance Participations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value	[1]	74,886,023	80,236,312
Short Term Investments [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value	[1]	7,933,928	13,644,683
Equity Warrants [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		1,080,222	1,080,222
Level 3 [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		366,279,562	372,977,743
Level 3 [Member] | Senior Secured Term Loans [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		84,349,839	88,858,707
Level 3 [Member] | Senior Secured Term Loan Participations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		198,029,550	189,157,819
Level 3 [Member] | Senior Secured Trade Finance Participations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		74,886,023	80,236,312
Level 3 [Member] | Short Term Investments [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		7,933,928	13,644,683
Level 3 [Member] | Equity Warrants [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments, fair value		$ 1,080,222	$ 1,080,222

[1] Refer to Notes 2, 3 and 4 of the consolidated financial statements for additional information on the Company’s investments.