Fair Value Measurements - Summary of Investments Classified as Level 3 (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Net change in unrealized appreciation (depreciation) on investments	$ (1,052,185)	$ 243,836	$ (9,730,903)	$ (1,903,180)
Level 3 [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment owned at fair value, beginning balance			340,298,376
Purchases of investments			24,250,000
Maturities or Prepayments of investments			(30,132,424)
Accretion of discounts / Payment-in-kind interest			5,908,451
Net change in unrealized appreciation (depreciation) on investments			(9,730,903)	$ (1,903,180)
Investment owned at Fair value, ending balance	330,593,500		330,593,500
Level 3 [Member] | Senior Secured Term Loans [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment owned at fair value, beginning balance			83,353,208
Purchases of investments			13,250,000
Maturities or Prepayments of investments			(627,901)
Accretion of discounts / Payment-in-kind interest			3,440,108
Investment owned at Fair value, ending balance	99,415,415		99,415,415
Level 3 [Member] | Senior Secured Term Loan Participations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment owned at fair value, beginning balance			180,500,425
Maturities or Prepayments of investments			(18,238,360)
Accretion of discounts / Payment-in-kind interest			2,468,343
Net change in unrealized appreciation (depreciation) on investments			(6,305,500)
Investment owned at Fair value, ending balance	158,424,908		158,424,908
Level 3 [Member] | Senior Secured Trade Finance Participations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment owned at fair value, beginning balance			71,606,458
Purchases of investments			7,000,000
Maturities or Prepayments of investments			(7,266,163)
Net change in unrealized appreciation (depreciation) on investments			(3,544,799)
Investment owned at Fair value, ending balance	67,795,496		67,795,496
Level 3 [Member] | Short Term and Other Investments [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment owned at fair value, beginning balance			3,758,063
Purchases of investments			4,000,000
Maturities or Prepayments of investments			(4,000,000)
Investment owned at Fair value, ending balance	3,758,063		3,758,063
Level 3 [Member] | Equity Warrants [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investment owned at fair value, beginning balance			1,080,222
Net change in unrealized appreciation (depreciation) on investments			119,396
Investment owned at Fair value, ending balance	$ 1,199,618		$ 1,199,618