Summary of Significant Accounting Policies - Summary of Investments Using Significant Unobservable Input (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Fair value	$ 49,413,286	$ 53,293,715
Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Fair value	$ 38,516,582	$ 28,500,789
Asset-Backed Securities [Member] | Asset Backed Securities One [Member] | Grayson Investor Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Asset-Backed Securities	Asset-Backed Securities
Fair value	$ 84	$ 7,023
Asset-Backed Securities [Member] | Asset Backed Securities One [Member] | PAMCO CLO 1997-1A B [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Asset-Backed Securities
Fair value		$ 13
Common Stocks [Member] | Common Stock One [Member] | American Banknote Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Common Stocks	Common Stocks
Fair value	$ 3,536,250	$ 1,732,500
Common Stocks [Member] | Common Stock One [Member] | IQHQ, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Common Stocks	Common Stocks
Fair value	$ 2,533,000	$ 2,359,000
Common Stocks [Member] | Common Stock One [Member] | MPM Holdings, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Common Stocks
Fair value	$ 42,500
Common Stocks [Member] | Common Stock One [Member] | MidWave Wireless, Inc. (fka Terrestar Corp.) [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Common Stocks
Fair value	$ 4,732,181
Common Stocks [Member] | Common Stock One [Member] | TerreStar Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Common Stocks
Fair value		$ 5,114,214
Common Stocks [Member] | Common Stock One [Member] | Wayne Services Legacy, Inc [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Common Stocks
Fair value		$ 2,269
LLC Interests [Member] | LLC Interests One [Member] | NexPoint Capital REIT, LLC [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	LLC Interests	LLC Interests
Fair value	$ 7,014,774	$ 1,176,024
LLC Interests [Member] | LLC Interests One [Member] | SFR WLIF III, LLC [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	LLC Interests	LLC Interests
Fair value	$ 338,973	$ 424,468
LLC Interests [Member] | LLC Interests One [Member] | US Gaming, LLC [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	LLC Interests	LLC Interests
Fair value	$ 3,016,752	$ 3,088,750
Preferred Stocks [Member] | Preferred Stocks One [Member] | Apnimed, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Preferred Stocks	Preferred Stocks
Fair value	$ 1,644,435	$ 1,499,989
Preferred Stocks [Member] | Series B Preferred Stock [Member] | Sapience Therapeutics, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Preferred Stocks	Preferred Stocks
Fair value	$ 4,452,382	$ 4,549,525
Preferred Stocks [Member] | Series B One Preferred Stock [Member] | Sapience Therapeutics, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Preferred Stocks	Preferred Stocks
Fair value	$ 3,611,111	$ 3,677,777
Preferred Stocks [Member] | Series C Two Preferred Stock [Member] | Apnimed, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Preferred Stocks	Preferred Stocks
Fair value	$ 928,197	$ 799,994
Senior Secured Loans [Member] | NexPoint Capital REIT, LLC [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans
Fair value	$ 463,314
Senior Secured Loans [Member] | PlantSwitch, Inc. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans
Fair value	$ 2,000,000
Senior Secured Loans [Member] | Senior Secured Loans One [Member] | MidWave Wireless, Inc. (fka Terrestar Corp.) [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans
Fair value	$ 912,118
Senior Secured Loans [Member] | Senior Secured Loans One [Member] | CCS Medical, Inc [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans	Senior Secured Loans
Fair value	$ 3,000,000	$ 3,000,000
Senior Secured Loans [Member] | Senior Secured Loans One [Member] | TerreStar Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Senior Secured Loans
Fair value		$ 810,953
Senior Secured Loans [Member] | Senior Secured Loans Two [Member] | MidWave Wireless, Inc. (fka Terrestar Corp.) [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans
Fair value	$ 215,938
Senior Secured Loans [Member] | Senior Secured Loans Two [Member] | TerreStar Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Senior Secured Loans
Fair value		$ 191,988
Senior Secured Loans [Member] | Senior Secured Loans Three [Member] | MidWave Wireless, Inc. (fka Terrestar Corp.) [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans
Fair value	$ 38,579
Senior Secured Loans [Member] | Senior Secured Loans Three [Member] | TerreStar Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Senior Secured Loans
Fair value		$ 34,300
Senior Secured Loans [Member] | Senior Secured Loans Four [Member] | MidWave Wireless, Inc. (fka Terrestar Corp.) [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment	Senior Secured Loans
Fair value	$ 35,994
Senior Secured Loans [Member] | Senior Secured Loans Four [Member] | TerreStar Corp. [Member] | Level 3 [Member]
Disclosure In Tabular Form Of Investments Using Significant Unobservable Input [Line Items]
Description of type of investment		Senior Secured Loans
Fair value		$ 32,002