Investments - Schedule of Investment by Geographical Classification (Detail) - USD ($)		6 Months Ended	12 Months Ended
		Jun. 30, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Fair Value		$ 366,279,562	$ 372,977,743
Percentage of Total Investments		100.00%	100.00%
Argentina [Member]
Schedule of Investments [Line Items]
Fair Value	[1]	$ 24,308,298	$ 24,841,309
Percentage of Total Investments	[1]	6.60%	6.70%
Botswana [Member]
Schedule of Investments [Line Items]
Fair Value		$ 4,740,000	$ 4,740,000
Percentage of Total Investments		1.30%	1.30%
Brazil [Member]
Schedule of Investments [Line Items]
Fair Value		$ 25,863,901	$ 22,183,252
Percentage of Total Investments		7.10%	5.90%
Cabo Verde [Member]
Schedule of Investments [Line Items]
Fair Value		$ 12,540,286	$ 16,459,362
Percentage of Total Investments		3.40%	4.40%
Cameroon [Member]
Schedule of Investments [Line Items]
Fair Value		$ 10,718,201	$ 10,718,201
Percentage of Total Investments		2.90%	2.90%
Chile [Member]
Schedule of Investments [Line Items]
Fair Value		$ 4,042,146	$ 9,136,558
Percentage of Total Investments		1.10%	2.40%
China [Member]
Schedule of Investments [Line Items]
Fair Value			$ 10,000,000
Percentage of Total Investments		0.00%	2.70%
Colombia [Member]
Schedule of Investments [Line Items]
Fair Value		$ 23,862,002	$ 24,434,056
Percentage of Total Investments		6.50%	6.60%
Croatia [Member]
Schedule of Investments [Line Items]
Fair Value		$ 8,460,514	$ 8,262,375
Percentage of Total Investments		2.30%	2.20%
Ecuador [Member]
Schedule of Investments [Line Items]
Fair Value		$ 35,838	$ 35,838
Percentage of Total Investments		0.00%	0.00%
Ghana [Member]
Schedule of Investments [Line Items]
Fair Value		$ 52,672,970	$ 52,027,237
Percentage of Total Investments		14.40%	13.90%
Guatemala [Member]
Schedule of Investments [Line Items]
Fair Value		$ 10,504	$ 662,525
Percentage of Total Investments		0.00%	0.20%
Hong Kong [Member]
Schedule of Investments [Line Items]
Fair Value		$ 49,500,000	$ 37,000,000
Percentage of Total Investments		13.50%	9.90%
Jersey [Member]
Schedule of Investments [Line Items]
Fair Value		$ 18,572,500	$ 18,515,500
Percentage of Total Investments		5.10%	5.00%
Kenya [Member]
Schedule of Investments [Line Items]
Fair Value		$ 13,233,109	$ 12,970,938
Percentage of Total Investments		3.60%	3.50%
Malaysia [Member]
Schedule of Investments [Line Items]
Fair Value		$ 15,000,000	$ 15,000,000
Percentage of Total Investments		4.10%	4.00%
Mauritius [Member]
Schedule of Investments [Line Items]
Fair Value		$ 2,468,756	$ 2,500,000
Percentage of Total Investments		0.70%	0.70%
Mexico [Member]
Schedule of Investments [Line Items]
Fair Value		$ 24,042,376	$ 22,447,343
Percentage of Total Investments		6.60%	6.00%
Morocco [Member]
Schedule of Investments [Line Items]
Fair Value		$ 7,530,616	$ 7,632,234
Percentage of Total Investments		2.10%	2.00%
Namibia [Member]
Schedule of Investments [Line Items]
Fair Value		$ 16,425,961	$ 16,083,083
Percentage of Total Investments		4.50%	4.30%
Netherlands [Member]
Schedule of Investments [Line Items]
Fair Value		$ 11,438,615	$ 4,000,000
Percentage of Total Investments		3.10%	1.10%
New Zealand [Member]
Schedule of Investments [Line Items]
Fair Value		$ 6,840,000	$ 6,840,000
Percentage of Total Investments		1.90%	1.80%
Nigeria [Member]
Schedule of Investments [Line Items]
Fair Value		$ 14,414,603	$ 15,782,226
Percentage of Total Investments		3.90%	4.20%
Peru [Member]
Schedule of Investments [Line Items]
Fair Value		$ 4,465,132	$ 4,465,132
Percentage of Total Investments		1.20%	1.20%
Romania [Member]
Schedule of Investments [Line Items]
Fair Value		$ 1,975,009	$ 1,917,097
Percentage of Total Investments		0.50%	0.50%
Singapore [Member]
Schedule of Investments [Line Items]
Fair Value			$ 3,737,737
Percentage of Total Investments			1.00%
South Africa [Member]
Schedule of Investments [Line Items]
Fair Value		$ 1,564,870	$ 6,719,642
Percentage of Total Investments		0.40%	1.80%
United Arab Emirates [Member]
Schedule of Investments [Line Items]
Fair Value		$ 803,254	$ 803,254
Percentage of Total Investments		0.20%	0.20%
Uganda [Member]
Schedule of Investments [Line Items]
Fair Value		$ 4,300,000	$ 4,300,000
Percentage of Total Investments		1.20%	1.20%
Zambia [Member]
Schedule of Investments [Line Items]
Fair Value		$ 1,516,173	$ 3,250,844
Percentage of Total Investments		0.40%	0.90%
Other [Member]
Schedule of Investments [Line Items]
Fair Value		$ 4,933,928	$ 5,512,000
Percentage of Total Investments		1.40%	1.50%

[1] All of the Company’s investments in Argentina are Participations in trade finance facilities originated by IIG TOF B.V., a subsidiary of a fund advised by the Company’s sub-advisor, IIG. See Note 3 “Watch List Investments” for further information.