Investments - Schedule of Watch List Investments (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Schedule of Investments [Line Items]
Fair Value	$ 327,269,549		$ 327,269,549		$ 340,298,376
Interest receivable	24,612,389		24,612,389		16,501,872
Non-Accrual Status [Member]
Schedule of Investments [Line Items]
Fair Value	25,906,728		25,906,728		38,261,499
Interest not accrued on Investments on Non-Accrual status	660,001	$ 1,177,023	2,667,811	$ 3,419,981
Sub-advisory Agreement [Member]
Schedule of Investments [Line Items]
Principal Amount	140,750,052		140,750,052		73,412,152
Fair Value	112,675,257		112,675,257		59,366,598
Interest receivable	14,541,458		14,541,458		5,674,687
Sub-advisory Agreement [Member] | Non-Accrual Status [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	660,001	1,177,023	2,667,811	3,419,981
Sub-advisory Agreement [Member] | Usivale Industria E Commercio Ltda [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	2,851,296		2,851,296		2,851,296
Fair Value	2,577,164		2,577,164		2,577,164
Interest receivable	645,932		645,932		376,075
Sub-advisory Agreement [Member] | Helios Investment Partners, LLP [Member] | Trustco Group Holdings Ltd [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	17,352,309		17,352,309
Fair Value	15,057,045		15,057,045
Interest receivable	1,745,356		1,745,356
Sub-advisory Agreement [Member] | Helios Investment Partners, LLP [Member] | TRG Cape Verde Holdings Ltd [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	13,316,643		13,316,643
Fair Value	11,404,266		11,404,266
Interest receivable	1,570,400		1,570,400
Sub-advisory Agreement [Member] | Helios Investment Partners, LLP [Member] | Helios Maritime I [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	14,542,437		14,542,437
Fair Value	12,078,217		12,078,217
Interest receivable	3,387,579		3,387,579
Sub-advisory Agreement [Member] | IIG [Member] | Compania Argentina de Granos S.A. [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	12,500,000		12,500,000		12,500,000
Fair Value	9,679,636		9,679,636		9,839,958
Interest receivable	664,010		664,010
Sub-advisory Agreement [Member] | IIG [Member] | Compania Argentina de Granos S.A. [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status		333,819	330,191	990,573
Sub-advisory Agreement [Member] | IIG [Member] | Frigorifico Regional Industrias Alimentarias S.A. Sucursal Uruguay [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	9,000,000		9,000,000		9,000,000
Fair Value	6,361,679		6,361,679		6,240,961
Interest receivable	264,500		264,500		264,500
Sub-advisory Agreement [Member] | IIG [Member] | Frigorifico Regional Industrias Alimentarias S.A. Sucursal Uruguay [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	264,500	264,500	787,750	784,875
Sub-advisory Agreement [Member] | IIG [Member] | Sancor Cooperativas Unidas Ltda [Member] | Hybrid Income and Collateral Based Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	6,000,000		6,000,000		6,000,000
Fair Value	4,719,383		4,719,383		4,719,383
Interest receivable	768,240		768,240		442,805
Sub-advisory Agreement [Member] | IIG [Member] | Sancor Cooperativas Unidas Ltda [Member] | Non-Accrual Status [Member] | Hybrid Income and Collateral Based Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status			161,829
Sub-advisory Agreement [Member] | IIG [Member] | IIG TOF B.V. [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	6,000,000		6,000,000		6,000,000
Fair Value	3,758,063		3,758,063		3,758,063
Interest receivable	572,000		572,000		572,000
Sub-advisory Agreement [Member] | IIG [Member] | IIG TOF B.V. [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	134,167	134,167	399,583	398,125
Sub-advisory Agreement [Member] | IIG [Member] | Algodonera Avellaneda S.A [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	6,000,000		6,000,000		6,000,000
Fair Value	3,398,558		3,398,558		3,398,558
Interest receivable	778,500		778,500		778,500
Sub-advisory Agreement [Member] | IIG [Member] | Algodonera Avellaneda S.A [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	138,000	138,000	411,000	409,500
Sub-advisory Agreement [Member] | IIG [Member] | Functional Products Trading S.A [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	1,326,687		1,326,687		1,326,687
Fair Value	1,375,794		1,375,794		1,269,586
Interest receivable	220,881		220,881		220,882
Sub-advisory Agreement [Member] | IIG [Member] | Functional Products Trading S.A [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	36,956	36,956	110,064	36,956
Sub-advisory Agreement [Member] | IIG [Member] | Representaciones Saldana S.A. [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	35,838		35,838
Fair Value	35,838		35,838
Interest receivable	5,725		5,725
Sub-advisory Agreement [Member] | IIG [Member] | Procesos Fabriles S.A. [Member] | Collateral Based Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	881,800		881,800		881,800
Fair Value	10,504		10,504		10,504
Sub-advisory Agreement [Member] | IIG [Member] | Procesos Fabriles S.A. [Member] | Non-Accrual Status [Member] | Collateral Based Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	27,042	27,832	80,537	82,588
Sub-advisory Agreement [Member] | TransAsia Private Capital Ltd [Member] | Triton Metallics Pte Ltd | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	17,959,733		17,959,733
Fair Value	16,296,587		16,296,587
Interest receivable	137,691		137,691
Sub-advisory Agreement [Member] | TransAsia Private Capital Ltd [Member] | Conplex International Ltd. [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount					9,500,000
Fair Value					8,840,048
Interest receivable					482,667
Sub-advisory Agreement [Member] | TransAsia Private Capital Ltd [Member] | Conplex International Ltd. [Member] | Collateral Based Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	9,500,000		9,500,000
Fair Value	3,366,356		3,366,356
Interest receivable	1,312,945		1,312,945
Sub-advisory Agreement [Member] | AMC [Member] | Producam SA [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	13,243,285		13,243,285		10,413,683
Fair Value	13,254,796		13,254,796		9,687,887
Interest receivable					2,403,043
Sub-advisory Agreement [Member] | Scipion [Member] | Mac Z Group SARL [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	7,349,626		7,349,626		7,349,626
Fair Value	6,734,018		6,734,018		7,530,616
Interest receivable	2,254,833		2,254,833
Sub-advisory Agreement [Member] | Scipion [Member] | Mac Z Group SARL [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status		206,606	204,361	613,081
Sub-advisory Agreement [Member] | Scipion [Member] | Global Pharma Intelligence Sarl [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	648,430		648,430		803,254
Fair Value	648,430		648,430		803,254
Interest receivable	134,215		134,215		134,215
Sub-advisory Agreement [Member] | Scipion [Member] | Global Pharma Intelligence Sarl [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	24,194		77,831
Sub-advisory Agreement [Member] | Barak [Member] | Applewood Trading 199 Pty, Ltd [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	785,806		785,806		785,806
Fair Value	497,462		497,462		$ 690,616
Sub-advisory Agreement [Member] | Barak [Member] | Applewood Trading 199 Pty, Ltd [Member] | Non-Accrual Status [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Interest not accrued on Investments on Non-Accrual status	35,142	$ 35,143	104,665	$ 104,283
Sub-advisory Agreement [Member] | Alsis [Member] | Itelecom Holding Chile SPA [Member] | Income Approach [Member]
Schedule of Investments [Line Items]
Principal Amount	1,456,162		1,456,162
Fair Value	1,421,461		1,421,461
Interest receivable	$ 78,651		$ 78,651