Consolidated Schedule of Investments (Parenthetical) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2023		Mar. 31, 2022	Dec. 31, 2022
Derivative [Line Items]
Qualifying assets, percent of total assets		76.70%			77.50%
Unfunded commitment with amortized cost		$ 2,500			$ 2,500
Investment company, financial commitment fair value		2,500			2,500
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	2,047,115
Net realized gain (loss) on investments:		(20,207)		$ (29,044)
Net change in unrealized appreciation (depreciation) on investments:		(30,473)		215,281
Fair Value, ending balance		1,742,661	[3],[4],[5]		2,047,115	[1],[2]
Paid-in-kind interest income		4,502		5,128
Non-controlled/affiliated
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		65,777		175,908	175,908
Gross Additions		139	[6]		9,273	[7]
Gross Reductions		(35,746)	[8]		(158,530)	[9]
Net realized gain (loss) on investments:		(11,359)		(12,380)	43,136
Net change in unrealized appreciation (depreciation) on investments:		(2,561)		56,051	(4,010)
Fair Value, ending balance		16,250			65,777
Interest Income		157	[10]		3,219	[11]
Paid-in-kind interest income		24	[10]	35	105	[11]
Fee income	[11]				7,268
Dividend income		0		1,726	5,417
Controlled/affiliated
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		194,451		181,359	181,359
Gross Additions		173	[12]		7,154	[13]
Gross Reductions		(996)	[14]		(41,601)	[15]
Net realized gain (loss) on investments:		0			15,899
Net change in unrealized appreciation (depreciation) on investments:		(3,393)		23,727	31,640
Fair Value, ending balance		190,235			194,451
Interest Income		2,459	[16]		2,936	[17]
Paid-in-kind interest income		172	[16]	670	7,154	[17]
Dividend income		$ 0		735	$ 735	[17]
London Interbank Offered Rate (LIBOR)
Derivative [Line Items]
Investment, variable rate		5.19%			4.77%
Secured Overnight Financing Rate
Derivative [Line Items]
Investment, variable rate		4.91%			4.59%
Investment, Identifier [Axis]: AIRRO (Mauritius) Holdings II, Power 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[19],[20]	$ 23,519
Fair Value, ending balance		23,682	[3],[4],[5],[21],[22],[23]		$ 23,519	[1],[2],[18],[19],[20]
Investment, Identifier [Axis]: AIRRO (Mauritius) Holdings II, Power 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[19],[20],[24]	5,545
Fair Value, ending balance		5,542	[3],[4],[5],[21],[22],[23],[25]		5,545	[1],[2],[18],[19],[20],[24]
Investment, Identifier [Axis]: AIRRO (Mauritius) Holdings II, Warrants, Strike: $1.00, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[19],[20],[26],[27]	1,630
Fair Value, ending balance		1,381	[3],[4],[5],[21],[22],[23],[28]		1,630	[1],[2],[18],[19],[20],[26],[27]
Investment, Identifier [Axis]: Abaco Energy Technologies LLC, Common Equity, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27]	1,219
Fair Value, ending balance		1,313	[3],[4],[5],[21],[28]		1,219	[1],[2],[18],[26],[27]
Investment, Identifier [Axis]: Abaco Energy Technologies LLC, Preferred Equity, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27]	8,321
Fair Value, ending balance		9,175	[3],[4],[5],[21],[28]		8,321	[1],[2],[18],[26],[27]
Investment, Identifier [Axis]: Aethon III BR LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	20,138
Fair Value, ending balance		20,111	[3],[4],[5],[21]		20,138	[1],[2],[18],[27]
Investment, Identifier [Axis]: Aethon United BR LP, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[27]	40,221
Fair Value, ending balance		39,780	[3],[4],[5]		40,221	[1],[2],[27]
Investment, Identifier [Axis]: AirSwift Holdings, Ltd., Common Equity, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, ending balance	[3],[4],[5],[21],[23],[28]	3,413
Investment, Identifier [Axis]: Allied Downhole Technologies, LLC
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[30]	8,436	[29]	7,782	7,782
Gross Additions		113	[12],[29]		654	[13],[30]
Gross Reductions		(996)	[14],[29]		0	[15],[30]
Net realized gain (loss) on investments:		0	[29]		0	[30]
Net change in unrealized appreciation (depreciation) on investments:		0	[29]		0	[30]
Fair Value, ending balance	[29]	7,553			8,436	[30]
Interest Income		52	[16],[29]		0	[17],[30]
Paid-in-kind interest income		113	[16],[29]		654	[17],[30]
Dividend income	[17],[30]				0
Investment, Identifier [Axis]: Allied Downhole Technologies, LLC, Service & Equipment 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27],[31]	8,436
Fair Value, ending balance		7,553	[3],[4],[5],[21],[32]		8,436	[1],[2],[18],[27],[31]
Investment, Identifier [Axis]: Allied Downhole Technologies, LLC, Service & Equipment 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[24],[31]	2,500
Fair Value, ending balance		2,500	[3],[4],[5],[21],[25],[32]		2,500	[1],[2],[18],[24],[31]
Investment, Identifier [Axis]: Allied Wireline Services, LLC
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		63,888		46,339	46,339
Gross Additions		0	[12]		5,808	[13]
Gross Reductions		0	[14]		0	[15]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		0			11,741
Fair Value, ending balance		63,888			63,888
Interest Income		1,597	[16]		316	[17]
Paid-in-kind interest income		0	[16]		5,808	[17]
Dividend income	[17]				0
Investment, Identifier [Axis]: Allied Wireline Services, LLC, Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		10,463		0	0
Gross Additions		0	[12]		0	[13]
Gross Reductions		0	[14]		0	[15]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		1,922			10,463
Fair Value, ending balance		12,385			10,463
Interest Income		0	[16]		0	[17]
Paid-in-kind interest income		0	[16]		0	[17]
Dividend income	[17]				0
Investment, Identifier [Axis]: Allied Wireline Services, LLC, Common Equity, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[31],[33]	10,463
Fair Value, ending balance		12,385	[3],[4],[5],[21],[28],[32],[34]		10,463	[1],[2],[18],[26],[27],[31],[33]
Investment, Identifier [Axis]: Allied Wireline Services, LLC, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27],[31]	63,888
Fair Value, ending balance		63,888	[3],[4],[5],[21],[32]		63,888	[1],[2],[18],[27],[31]
Investment, Identifier [Axis]: Allied Wireline Services, LLC, Warrants
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		0	0
Gross Additions		0	[12]		0	[13]
Gross Reductions		0	[14]		0	[15]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		0			0
Fair Value, ending balance		0			0
Interest Income		0	[16]		0	[17]
Paid-in-kind interest income		0	[16]		0	[17]
Dividend income	[17]				0
Investment, Identifier [Axis]: Allied Wireline Services, LLC, Warrants, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[31],[33]	0
Fair Value, ending balance		0	[3],[4],[5],[21],[28],[32],[34]		0	[1],[2],[18],[26],[27],[31],[33]
Investment, Identifier [Axis]: Archrock Partners, L.P., Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[20],[27]	2,840
Fair Value, ending balance	[1],[2],[20],[27]				2,840
Investment, Identifier [Axis]: Arena Energy, LP, Contingent Value Rights, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27]	858
Fair Value, ending balance		514	[3],[4],[5],[21]		858	[1],[2],[18],[26],[27]
Investment, Identifier [Axis]: Ascent Resources Utica Holdings, LLC, Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[33]	52,340
Fair Value, ending balance		40,221	[3],[4],[5],[21],[28],[34]		52,340	[1],[2],[18],[26],[27],[33]
Investment, Identifier [Axis]: Brazos Delaware II LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	39,137
Fair Value, ending balance	[1],[2]				39,137
Investment, Identifier [Axis]: CPV Maryland, LLC, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	14,155
Fair Value, ending balance	[1],[2]				14,155
Investment, Identifier [Axis]: CPV Shore Holdings LLC, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	21,935
Fair Value, ending balance		21,874	[3],[4],[5]		21,935	[1],[2]
Investment, Identifier [Axis]: Cimarron Energy Holdco Inc., Common Equity, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27]	0
Fair Value, ending balance	[1],[2],[18],[26],[27]				0
Investment, Identifier [Axis]: Cimarron Energy Holdco Inc., Participation Option, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27]	0
Fair Value, ending balance	[1],[2],[18],[26],[27]				0
Investment, Identifier [Axis]: Cimarron Energy Inc., Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[35]	3,713
Fair Value, ending balance	[1],[2],[18],[26],[27],[35]				3,713
Investment, Identifier [Axis]: Citizen Energy Operating, LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	38,240
Fair Value, ending balance		37,380	[3],[4],[5],[21]		38,240	[1],[2],[18],[27]
Investment, Identifier [Axis]: Compass Power Generation LLC, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	31,384
Fair Value, ending balance		9,777	[3],[4],[5]		31,384	[1],[2]
Investment, Identifier [Axis]: Cox Oil Offshore, LLC, Volumetric Production Payments, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[36],[37]	20,683
Fair Value, ending balance		12,822	[3],[4],[5],[21],[38],[39]		20,683	[1],[2],[18],[36],[37]
Investment, Identifier [Axis]: EIF Van Hook Holdings, LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	26,075
Fair Value, ending balance		26,781	[3],[4],[5]		26,075	[1],[2]
Investment, Identifier [Axis]: ERA II Minerals, LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	36,656
Fair Value, ending balance		35,564	[3],[4],[5],[21]		36,656	[1],[2],[18],[27]
Investment, Identifier [Axis]: Earthstone Energy Holdings, LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[20]	10,920
Fair Value, ending balance		11,073	[3],[4],[5],[23]		10,920	[1],[2],[20]
Investment, Identifier [Axis]: Endeavor Energy Resources, L.P., Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[27]	23,306
Fair Value, ending balance	[1],[2],[27]				23,306
Investment, Identifier [Axis]: FR BR Holdings LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	81,361
Fair Value, ending balance		81,242	[3],[4],[5],[21]		81,361	[1],[2],[18],[27]
Investment, Identifier [Axis]: FR XIII PAA Holdings HoldCo, LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	17,406
Fair Value, ending balance		17,351	[3],[4],[5],[21]		17,406	[1],[2],[18]
Investment, Identifier [Axis]: GIP II Blue Holding LP, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	5,877
Fair Value, ending balance		5,792	[3],[4],[5]		5,877	[1],[2]
Investment, Identifier [Axis]: GWP Midstream Holdco, LLC, Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		5,044		0	0
Gross Additions		0	[6]		6,681	[7]
Gross Reductions		0	[8]		0	[9]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		(1,437)			(1,637)
Fair Value, ending balance		3,607			5,044
Interest Income		0	[10]		0	[11]
Paid-in-kind interest income		0	[10]		0	[11]
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: GWP Midstream Holdco, LLC, Common Equity, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[33],[40]	5,044
Fair Value, ending balance		3,607	[3],[4],[5],[21],[28],[34],[41]		5,044	[1],[2],[18],[26],[27],[33],[40]
Investment, Identifier [Axis]: GasLog Ltd., Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20]	14,010
Fair Value, ending balance		14,125	[3],[4],[5],[21],[23]		14,010	[1],[2],[18],[20]
Investment, Identifier [Axis]: Generation Bridge LLC, Power 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	7,385
Fair Value, ending balance		7,091	[3],[4],[5]		7,385	[1],[2]
Investment, Identifier [Axis]: Generation Bridge LLC, Power 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	162
Fair Value, ending balance		163	[3],[4],[5]		162	[1],[2]
Investment, Identifier [Axis]: Global Jet Capital Holdings, LP, Preferred Equity, Industrials 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27]	0
Fair Value, ending balance		0	[3],[4],[5],[21],[28]		0	[1],[2],[18],[26],[27]
Investment, Identifier [Axis]: Global Jet Capital Holdings, LP, Preferred Equity, Industrials 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[35]	9,377
Fair Value, ending balance		9,641	[3],[4],[5],[21],[28],[42]		9,377	[1],[2],[18],[26],[27],[35]
Investment, Identifier [Axis]: Goodnight Water Solutions, LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	14,819
Fair Value, ending balance		14,788	[3],[4],[5],[21]		14,819	[1],[2],[18]
Investment, Identifier [Axis]: Great Western Petroleum, LLC
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		58,055	58,055
Gross Additions	[7]				96
Gross Reductions	[9]				(55,096)
Net realized gain (loss) on investments:					1,087
Net change in unrealized appreciation (depreciation) on investments:					(4,142)
Fair Value, ending balance					0
Interest Income	[11]				2,649
Paid-in-kind interest income	[11]				0
Fee income	[11]				7,268
Dividend income					0
Investment, Identifier [Axis]: Great Western Petroleum, LLC, Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		40,731	40,731
Gross Additions	[7]				0
Gross Reductions	[9]				(84,871)
Net realized gain (loss) on investments:					54,081
Net change in unrealized appreciation (depreciation) on investments:					(9,941)
Fair Value, ending balance					0
Interest Income	[11]				0
Paid-in-kind interest income	[11]				0
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: Hamilton Intermediate Holdings, LLC, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	31,007
Fair Value, ending balance		31,996	[3],[4],[5],[21]		31,007	[1],[2],[18]
Investment, Identifier [Axis]: Hammerhead Resources Inc., Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[27]	35,118
Fair Value, ending balance		37,225	[3],[4],[5],[21],[23]		35,118	[1],[2],[18],[20],[27]
Investment, Identifier [Axis]: Harvest Oil & Gas Corp., Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		810		2,836	2,836
Gross Additions		0	[6]		0	[7]
Gross Reductions		(506)	[8]		(743)	[9]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		506			(1,283)
Fair Value, ending balance		810			810
Interest Income		0	[10]		0	[11]
Paid-in-kind interest income		0	[10]		0	[11]
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: Harvest Oil & Gas Corp., Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[26],[27],[40]	810
Fair Value, ending balance		810	[3],[4],[5],[21],[28],[41]		810	[1],[2],[26],[27],[40]
Investment, Identifier [Axis]: Limetree Bay Energy, LLC
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		3,166	3,166
Gross Additions	[7]				0
Gross Reductions	[9]				(1,587)
Net realized gain (loss) on investments:					(12,756)
Net change in unrealized appreciation (depreciation) on investments:					11,177
Fair Value, ending balance					0
Interest Income	[11]				0
Paid-in-kind interest income	[11]				0
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: Limetree Bay Energy, LLC, Class A Units
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		1,885		6,046	6,046
Gross Additions		83	[6]		1,795	[7]
Gross Reductions		0	[8]		0	[9]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		(1,029)			(5,956)
Fair Value, ending balance		939			1,885
Interest Income		0	[10]		0	[11]
Paid-in-kind interest income		0	[10]		0	[11]
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: Limetree Bay Energy, LLC, Class A Units, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[40]	1,885
Fair Value, ending balance		939	[3],[4],[5],[21],[28],[41]		1,885	[1],[2],[18],[26],[27],[40]
Investment, Identifier [Axis]: MB Precision Investment Holdings LLC, Class A-2 Units, Industrials
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[33]	0
Fair Value, ending balance	[1],[2],[18],[26],[27],[33]				0
Investment, Identifier [Axis]: MECO IV Holdco, LLC
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		22,745	22,745
Gross Additions	[13]				455
Gross Reductions	[15]				(23,200)
Net realized gain (loss) on investments:					0
Net change in unrealized appreciation (depreciation) on investments:					0
Fair Value, ending balance					0
Interest Income	[17]				0
Paid-in-kind interest income	[17]				455
Dividend income	[17]				0
Investment, Identifier [Axis]: MECO IV Holdco, LLC, Class A-1 Units
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		4,181	4,181
Gross Additions	[13]				0
Gross Reductions	[15]				(18,060)
Net realized gain (loss) on investments:					15,899
Net change in unrealized appreciation (depreciation) on investments:					(2,020)
Fair Value, ending balance					0
Interest Income	[17]				0
Paid-in-kind interest income	[17]				0
Dividend income	[17]				0
Investment, Identifier [Axis]: Maverick Natural Resources, LLC, Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27],[33]	312,372
Fair Value, ending balance		278,760	[3],[4],[5],[21],[34]		312,372	[1],[2],[18],[27],[33]
Investment, Identifier [Axis]: Medallion Midland Acquisition LP, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	7,862
Fair Value, ending balance	[1],[2]				7,862
Investment, Identifier [Axis]: Meritage Midstream Services II, LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, ending balance	[3],[4],[5],[21]	24,500
Investment, Identifier [Axis]: Moss Creek Resources, LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[27]	10,561
Fair Value, ending balance		10,856	[3],[4],[5]		10,561	[1],[2],[27]
Investment, Identifier [Axis]: NGL Energy Partners, LP, Preferred Equity, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27],[35]	125,000
Fair Value, ending balance		134,138	[3],[4],[5],[21],[23],[28],[42]		125,000	[1],[2],[18],[20],[26],[27],[35]
Investment, Identifier [Axis]: NGL Energy Partners, LP, Warrants (Par), Strike: $13.56, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27]	3
Fair Value, ending balance		105	[3],[4],[5],[21],[23],[28]		3	[1],[2],[18],[20],[26],[27]
Investment, Identifier [Axis]: NGL Energy Partners, LP, Warrants (Par), Strike: $14.54, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27]	10
Fair Value, ending balance		441	[3],[4],[5],[21],[23],[28]		10	[1],[2],[18],[20],[26],[27]
Investment, Identifier [Axis]: NGL Energy Partners, LP, Warrants (Premium), Strike: $16.27, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27]	2
Fair Value, ending balance		113	[3],[4],[5],[21],[23],[28]		2	[1],[2],[18],[20],[26],[27]
Investment, Identifier [Axis]: NGL Energy Partners, LP, Warrants (Premium), Strike: $17.45, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27]	8
Fair Value, ending balance		449	[3],[4],[5],[21],[23],[28]		8	[1],[2],[18],[20],[26],[27]
Investment, Identifier [Axis]: NRG Energy, Inc., Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[20]	14,401
Fair Value, ending balance		12,917	[3],[4],[5],[23]		14,401	[1],[2],[20]
Investment, Identifier [Axis]: NuStar, Preferred Equity, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[27]	83,590
Fair Value, ending balance		83,272	[3],[4],[5],[21],[23]		83,590	[1],[2],[18],[20],[27]
Investment, Identifier [Axis]: OE2 North, LLC, Midstream 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	18,847
Fair Value, ending balance		19,243	[3],[4],[5],[21]		18,847	[1],[2],[18]
Investment, Identifier [Axis]: OE2 North, LLC, Midstream 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[24]	11,455
Fair Value, ending balance		10,968	[3],[4],[5],[21],[25]		11,455	[1],[2],[18],[24]
Investment, Identifier [Axis]: Oryx Midstream Services Permian Basin LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[27]	32,026
Fair Value, ending balance		25,885	[3],[4],[5]		32,026	[1],[2],[27]
Investment, Identifier [Axis]: Parkway Generation LLC, Power 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	5,700
Fair Value, ending balance		5,577	[3],[4],[5]		5,700	[1],[2]
Investment, Identifier [Axis]: Parkway Generation LLC, Power 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	43,285
Fair Value, ending balance		42,431	[3],[4],[5]		43,285	[1],[2]
Investment, Identifier [Axis]: Peak Exploration & Production, LLC, Upstream 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	13,394
Fair Value, ending balance	[1],[2],[18],[27]				13,394
Investment, Identifier [Axis]: Peak Exploration & Production, LLC, Upstream 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[24]	1,488
Fair Value, ending balance	[1],[2],[18],[24]				1,488
Investment, Identifier [Axis]: Permian Production Holdings, LLC
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		4,767		7,889	7,889
Gross Additions		56	[6]		697	[7]
Gross Reductions		0	[8]		(3,674)	[9]
Net realized gain (loss) on investments:		0			551
Net change in unrealized appreciation (depreciation) on investments:		(32)			(696)
Fair Value, ending balance		4,791			4,767
Interest Income		157	[10]		570	[11]
Paid-in-kind interest income		24	[10]		105	[11]
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: Permian Production Holdings, LLC, Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		11,420		8,829	8,829
Gross Additions		0	[6]		4	[7]
Gross Reductions		0	[8]		0	[9]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		(5,317)			2,587
Fair Value, ending balance		6,103			11,420
Interest Income		0	[10]		0	[11]
Paid-in-kind interest income		0	[10]		0	[11]
Fee income	[11]				0
Dividend income					1,726
Investment, Identifier [Axis]: Permian Production Holdings, LLC, Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27],[33],[40]	11,420
Fair Value, ending balance		6,103	[3],[4],[5],[21],[28],[34],[41]		11,420	[1],[2],[18],[27],[33],[40]
Investment, Identifier [Axis]: Permian Production Holdings, LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27],[40]	4,767
Fair Value, ending balance		4,791	[3],[4],[5],[21],[41]		4,767	[1],[2],[18],[27],[40]
Investment, Identifier [Axis]: Permian Resources Operating LLC, Upstream 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	25,703
Fair Value, ending balance	[1],[2]				25,703
Investment, Identifier [Axis]: Permian Resources Operating LLC, Upstream 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[27]	4,473
Fair Value, ending balance	[1],[2],[27]				4,473
Investment, Identifier [Axis]: Pinnacle Midland Gas Holdco LLC, Midstream 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	9,310
Fair Value, ending balance		9,314	[3],[4],[5],[21]		9,310	[1],[2],[18]
Investment, Identifier [Axis]: Pinnacle Midland Gas Holdco LLC, Midstream 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[24]	2,461
Fair Value, ending balance		2,462	[3],[4],[5],[21],[25]		2,461	[1],[2],[18],[24]
Investment, Identifier [Axis]: Plainfield Renewable Energy Holdings LLC, Letter of Credit, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[24]	0
Fair Value, ending balance		0	[3],[4],[5],[21],[25]		0	[1],[2],[18],[24]
Investment, Identifier [Axis]: Plainfield Renewable Energy Holdings LLC, Power 1
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	9,997
Fair Value, ending balance		9,468	[3],[4],[5],[21]		9,997	[1],[2],[18],[27]
Investment, Identifier [Axis]: Plainfield Renewable Energy Holdings LLC, Power 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	0
Fair Value, ending balance		0	[3],[4],[5],[21],[42]		0	[1],[2],[18],[27]
Investment, Identifier [Axis]: Potomac Energy Center, LLC, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	58,443
Fair Value, ending balance		56,878	[3],[4],[5],[21]		58,443	[1],[2],[18]
Investment, Identifier [Axis]: Ranger Oil Corp., Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[20]	29,678
Fair Value, ending balance	[1],[2],[20]				29,678
Investment, Identifier [Axis]: Ridgeback Resources Inc., Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		41,851		48,356	48,356
Gross Additions		0	[6]		0	[7]
Gross Reductions		(35,240)	[8]		(12,559)	[9]
Net realized gain (loss) on investments:		(11,359)			173
Net change in unrealized appreciation (depreciation) on investments:		4,748			5,881
Fair Value, ending balance		0			41,851
Interest Income		0	[10]		0	[11]
Paid-in-kind interest income		0	[10]		0	[11]
Fee income	[11]				0
Dividend income					3,691
Investment, Identifier [Axis]: Ridgeback Resources Inc., Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[27],[40],[43]	41,851
Fair Value, ending balance	[1],[2],[18],[20],[27],[40],[43]				41,851
Investment, Identifier [Axis]: ST EIP Holdings Inc., Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	10,074
Fair Value, ending balance		10,164	[3],[4],[5],[21]		10,074	[1],[2],[18]
Investment, Identifier [Axis]: Saturn Oil & Gas Inc., Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, ending balance	[3],[4],[5],[23],[28],[44]	3,220
Investment, Identifier [Axis]: Segreto Power Holdings, LLC, Preferred Equity, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[33],[35]	83,647
Fair Value, ending balance		86,037	[3],[4],[5],[21],[28],[34],[42]		83,647	[1],[2],[18],[26],[27],[33],[35]
Investment, Identifier [Axis]: SilverBow Resources, Inc., Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[27]	14,322
Fair Value, ending balance		14,297	[3],[4],[5],[21],[23]		14,322	[1],[2],[18],[20],[27]
Investment, Identifier [Axis]: Sitio Royalties Operating Partnership, LP, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[27]	19,256
Fair Value, ending balance		18,818	[3],[4],[5],[21],[23]		19,256	[1],[2],[18],[20],[27]
Investment, Identifier [Axis]: Suburban Propane Partners LP, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[20],[27]	6,461
Fair Value, ending balance	[1],[2],[20],[27]				6,461
Investment, Identifier [Axis]: Sustainable Infrastructure Investments, LLC 2
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		51,098		50,770	50,770
Gross Additions		0	[12]		0	[13]
Gross Reductions		0	[14]		0	[15]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		1,839			328
Fair Value, ending balance		52,937			51,098
Interest Income		0	[16]		0	[17]
Paid-in-kind interest income		0	[16]		0	[17]
Dividend income	[17]				735
Investment, Identifier [Axis]: Sustainable Infrastructure Investments, LLC, Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[31],[45]	51,098
Fair Value, ending balance		52,937	[3],[4],[5],[21],[23],[28],[32]		51,098	[1],[2],[18],[31],[45]
Investment, Identifier [Axis]: Swift Worldwide Resources Holdco Limited, Common Equity, Service & Equipment
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27],[46]	3,131
Fair Value, ending balance	[1],[2],[18],[20],[26],[27],[46]				3,131
Investment, Identifier [Axis]: Tallgrass Energy Partners, LP, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[27]	18,480
Fair Value, ending balance		9,250	[3],[4],[5]		18,480	[1],[2],[27]
Investment, Identifier [Axis]: Telpico, LLC, Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		0		0	0
Gross Additions		0	[6]		0	[7]
Gross Reductions		0	[8]		0	[9]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		0			0
Fair Value, ending balance		0			0
Interest Income		0	[10]		0	[11]
Paid-in-kind interest income		0	[10]		0	[11]
Fee income	[11]				0
Dividend income					0
Investment, Identifier [Axis]: Telpico, LLC, Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[33],[40]	0
Fair Value, ending balance		0	[3],[4],[5],[21],[28],[34],[41]		0	[1],[2],[18],[26],[27],[33],[40]
Investment, Identifier [Axis]: Tenrgys, LLC, Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[33]	6,801
Fair Value, ending balance		5,672	[3],[4],[5],[21],[28],[34]		6,801	[1],[2],[18],[26],[27],[33]
Investment, Identifier [Axis]: Tenrgys, LLC, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[27]	20,537
Fair Value, ending balance		20,691	[3],[4],[5],[21]		20,537	[1],[2],[18],[27]
Investment, Identifier [Axis]: Traverse Midstream Partners LLC, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2]	28,418
Fair Value, ending balance	[1],[2]				28,418
Investment, Identifier [Axis]: USA Compression Partners, LP, Common Equity, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[20],[26],[27]	1,655
Fair Value, ending balance		1,791	[3],[4],[5],[23]		1,655	[1],[2],[20],[26],[27]
Investment, Identifier [Axis]: USA Compression Partners, LP, Preferred Equity, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	90,479
Fair Value, ending balance		92,436	[3],[4],[5],[21],[23]		90,479	[1],[2],[18]
Investment, Identifier [Axis]: USA Compression Partners, LP, Warrants (Premium), Strike: $19.59, Midstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[20],[26],[27]	5,711
Fair Value, ending balance		6,380	[3],[4],[5],[21],[23],[28]		5,711	[1],[2],[18],[20],[26],[27]
Investment, Identifier [Axis]: Warren Resources, Inc.
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		23,584		23,688	23,688
Gross Additions		60	[12]		237	[13]
Gross Reductions		0	[14]		(341)	[15]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		0			0
Fair Value, ending balance		23,644			23,584
Interest Income		810	[16]		2,620	[17]
Paid-in-kind interest income		59	[16]		237	[17]
Dividend income	[17]				0
Investment, Identifier [Axis]: Warren Resources, Inc., Common Equity
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance		36,982		$ 25,854	25,854
Gross Additions		0	[12]		0	[13]
Gross Reductions		0	[14]		0	[15]
Net realized gain (loss) on investments:		0			0
Net change in unrealized appreciation (depreciation) on investments:		(7,154)			11,128
Fair Value, ending balance		29,828			36,982
Interest Income		0	[16]		0	[17]
Paid-in-kind interest income		0	[16]		0	[17]
Dividend income	[17]				0
Investment, Identifier [Axis]: Warren Resources, Inc., Common Equity, Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[26],[27],[31]	36,982
Fair Value, ending balance		29,828	[3],[4],[5],[21],[28],[32]		36,982	[1],[2],[18],[26],[27],[31]
Investment, Identifier [Axis]: Warren Resources, Inc., Upstream
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18],[31]	23,584
Fair Value, ending balance		23,644	[3],[4],[5],[21],[32]		23,584	[1],[2],[18],[31]
Investment, Identifier [Axis]: Wattbridge Inc., Power
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Fair Value, beginning balance	[1],[2],[18]	41,880
Fair Value, ending balance		$ 41,263	[3],[4],[5],[21]		$ 41,880	[1],[2],[18]

[1] Security may be an obligation of one or more entities affiliated with the named company.

[2] See Note 8 for additional information regarding the fair value of the Company’s financial instruments.

[3] Security may be an obligation of one or more entities affiliated with the named company.

[4] Security or portion thereof is pledged as collateral supporting the amounts outstanding under the Senior Secured Notes with JPMorgan Chase Bank, N.A. (see Note 9).

[5] See Note 8 for additional information regarding the fair value of the Company’s financial instruments.

[6] (1)    Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category.

[7] Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category.

[8] (2)    Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category.

[9] Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category.

[10] (3)    Interest and PIK income presented for the three months ended March 31, 2023.

[11] Interest, PIK, fee and dividend income presented for the year ended December 31, 2022.

[12] (1)    Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category.

[13] Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category.

[14] (2)    Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category.

[15] Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category.

[16] (3)    Interest and PIK income presented for the three months ended March 31, 2023.

[17] Interest, PIK and dividend income presented for the year ended December 31, 2022.

[18] Security is classified as Level 3 in the Company’s fair value hierarchy (see Note 8).

[19] Security or portion thereof held within FS Power Investments II, LLC, a wholly-owned subsidiary of the Company.

[20] The investment is not a qualifying asset under the Investment Company Act of 1940, as amended, or the 1940 Act. A business development company may not acquire any asset other than a qualifying asset, unless, at the time the acquisition is made, qualifying assets represent at least 70% of the business development company’s total assets. As of December 31, 2022, 77.5% of the Company’s total assets represented qualifying assets.

[21] Security is classified as Level 3 in the Company’s fair value hierarchy (see Note 8).

[22] Security or portion thereof held within FS Power Investments II, LLC, a wholly-owned subsidiary of the Company.

[23] The investment is not a qualifying asset under the Investment Company Act of 1940, as amended, or the 1940 Act. A business development company may not acquire any asset other than a qualifying asset, unless, at the time the acquisition is made, qualifying assets represent at least 70% of the business development company’s total assets. As of March 31, 2023, 76.7% of the Company’s total assets represented qualifying assets.

[24] Security is an unfunded commitment. The stated rate reflects the spread disclosed at the time of commitment and may not indicate the actual rate received upon funding.

[25] Security is an unfunded commitment. The stated rate reflects the spread disclosed at the time of commitment and may not indicate the actual rate received upon funding.

[26] Security is non-income producing.

[27] Security or portion thereof is pledged as collateral supporting the amounts outstanding under the Senior Secured Notes with JPMorgan Chase Bank, N.A. (see Note 9).

[28] Security is non-income producing.

[29] (4)    Security includes a partially unfunded commitment with amortized cost of $2,500 and fair value of $2,500.

[30] Security includes a partially unfunded commitment with amortized cost of $2,500 and fair value of $2,500.

[31] Under the 1940 Act, the Company generally is deemed to “control” a portfolio company if it owns more than 25% of the portfolio company’s voting securities or it has the power to exercise control over the management or policies of such portfolio company. As of December 31, 2022, the Company held investments in portfolio companies of which it is deemed to be an “affiliated person” of and deemed to “control.” The following table presents certain information with respect to investments in portfolio companies of which the Company was deemed to be an affiliated person and deemed to control as of December 31, 2022: Portfolio Company Fair Value at December 31, 2021 Gross Additions(1) Gross Reductions(2) Net Realized Gain (Loss)Net Change in Unrealized Appreciation (Depreciation) Fair Value at December 31, 2022 Interest Income(3) PIK Income(3) Dividend Income(3) Senior Secured Loans—First Lien Allied Downhole Technologies, LLC(4) $7,782 $654 $— $— $— $8,436 $— $654 $— Allied Wireline Services, LLC46,339 5,808 — — 11,741 63,888 316 5,808 — MECO IV Holdco, LLC22,745 455 (23,200)— — — — 455 — Warren Resources, Inc.23,688 237 (341)— — 23,584 2,620 237 — Sustainable Infrastructure Investments, LLCSustainable Infrastructure Investments, LLC50,770 — — — 328 51,098 — — 735 Equity/OtherAllied Wireline Services, LLC, Common Equity— — — — 10,463 10,463 — — — Allied Wireline Services, LLC, Warrants— — — — — — — — — MECO IV Holdco, LLC, Class A-1 Units4,181 — (18,060)15,899 (2,020)— — — — Warren Resources, Inc., Common Equity25,854 — — — 11,128 36,982 — — — $181,359 $7,154 $(41,601)$15,899 $31,640 $194,451 $2,936 $7,154 $735  _____________ (1)    Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category. (2)    Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category. (3)    Interest, PIK and dividend income presented for the year ended December 31, 2022. (4)    Security includes a partially unfunded commitment with amortized cost of $2,500 and fair value of $2,500.

[32] Under the 1940 Act, the Company generally is deemed to “control” a portfolio company if it owns more than 25% of the portfolio company’s voting securities or it has the power to exercise control over the management or policies of such portfolio company. As of March 31, 2023, the Company held investments in portfolio companies of which it is deemed to be an “affiliated person” of and deemed to “control.” The following table presents certain information with respect to investments in portfolio companies of which the Company was deemed to be an affiliated person and deemed to control as of March 31, 2023: Portfolio Company Fair Value at December 31, 2022 Gross Additions(1) Gross Reductions(2) Net Realized Gain (Loss)Net Change in Unrealized Appreciation (Depreciation) Fair Value at March 31, 2023 Interest Income(3) PIK Income(3) Senior Secured Loans—First Lien Allied Downhole Technologies, LLC(4) $8,436 $113 $(996)$— $— $7,553 $52 $113 Allied Wireline Services, LLC63,888 — — — — 63,888 1,597 — Warren Resources, Inc.23,584 60 — — — 23,644 810 59 Sustainable Infrastructure Investments, LLCSustainable Infrastructure Investments, LLC51,098 — — — 1,839 52,937 — — Equity/OtherAllied Wireline Services, LLC, Common Equity10,463 — — — 1,922 12,385 — — Allied Wireline Services, LLC, Warrants— — — — — — — — Warren Resources, Inc., Common Equity36,982 — — — (7,154)29,828 — — $194,451 $173 $(996)$— $(3,393)$190,235 $2,459 $172  _____________ (1)    Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category. (2)    Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category. (3)    Interest and PIK income presented for the three months ended March 31, 2023. (4)    Security includes a partially unfunded commitment with amortized cost of $2,500 and fair value of $2,500.

[33] Security held within FSEP Investments, Inc., a wholly-owned subsidiary of the Company.

[34] Security held within FSEP Investments, Inc., a wholly-owned subsidiary of the Company.

[35] Security was on non-accrual status as of December 31, 2022.

[36] Investment is a real property interest and is included with Senior Secured Loans—First Lien to facilitate comparison with other investments.

[37] Security held within EP Northern Investments, LLC, a wholly-owned subsidiary of the Company.

[38] Investment is a real property interest and is included with Senior Secured Loans—First Lien to facilitate comparison with other investments.

[39] Security held within EP Northern Investments, LLC, a wholly-owned subsidiary of the Company.

[40] Under the 1940 Act, the Company generally is deemed to be an “affiliated person” of a portfolio company if it owns 5% or more of the portfolio company’s voting securities and generally is deemed to “control” a portfolio company if it owns more than 25% of the portfolio company’s voting securities or it has the power to exercise control over the management or policies of such portfolio company. As of December 31, 2022, the Company held investments in portfolio companies of which it is deemed to be an “affiliated person” but is not deemed to “control”. The following table presents certain information with respect to investments in portfolio companies of which the Company was deemed to be an affiliated person as of December 31, 2022: Portfolio Company Fair Value at December 31, 2021 Gross Additions(1) Gross Reductions(2) Net Realized Gain (Loss)Net Change in Unrealized Appreciation (Depreciation) Fair Value at December 31, 2022 Interest Income(3) PIK Income(3) Fee Income(3) Dividend Income(3) Senior Secured Loans—First LienLimetree Bay Energy, LLC$3,166 $— $(1,587)$(12,756)$11,177 $— $— $— $— $— Permian Production Holdings, LLC7,889 697 (3,674)551 (696)4,767 570 105 — — Senior Secured BondsGreat Western Petroleum, LLC58,055 96 (55,096)1,087 (4,142)— 2,649 — 7,268 — Equity/OtherGreat Western Petroleum, LLC, Common Equity40,731 — (84,871)54,081 (9,941)— — — — — GWP Midstream Holdco, LLC, Common Equity— 6,681 — — (1,637)5,044 — — — — Harvest Oil & Gas Corp., Common Equity2,836 — (743)— (1,283)810 — — — — Limetree Bay Energy, LLC, Class A Units6,046 1,795 — — (5,956)1,885 — — — — Permian Production Holdings, LLC, Common Equity8,829 4 — — 2,587 11,420 — — — 1,726 Ridgeback Resources Inc., Common Equity48,356 — (12,559)173 5,881 41,851 — — — 3,691 Telpico, LLC, Common Equity— — — — — — — — — — $175,908 $9,273 $(158,530)$43,136 $(4,010)$65,777 $3,219 $105 $7,268 $5,417  _____________ (1)    Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category. (2)    Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category. (3)    Interest, PIK, fee and dividend income presented for the year ended December 31, 2022.

[41] Under the 1940 Act, the Company generally is deemed to be an “affiliated person” of a portfolio company if it owns 5% or more of the portfolio company’s voting securities and generally is deemed to “control” a portfolio company if it owns more than 25% of the portfolio company’s voting securities or it has the power to exercise control over the management or policies of such portfolio company. As of March 31, 2023, the Company held investments in portfolio companies of which it is deemed to be an “affiliated person” but is not deemed to “control”. The following table presents certain information with respect to investments in portfolio companies of which the Company was deemed to be an affiliated person as of March 31, 2023: Portfolio Company Fair Value at December 31, 2022 Gross Additions(1) Gross Reductions(2) Net Realized Gain (Loss)Net Change in Unrealized Appreciation (Depreciation) Fair Value at March 31, 2023 Interest Income(3) PIK Income(3) Senior Secured Loans—First LienPermian Production Holdings, LLC$4,767 $56 $— $— $(32)$4,791 $157 $24 Equity/OtherGWP Midstream Holdco, LLC, Common Equity5,044 — — — (1,437)3,607 — — Harvest Oil & Gas Corp., Common Equity810 — (506)— 506 810 — — Limetree Bay Energy, LLC, Class A Units1,885 83 — — (1,029)939 — — Permian Production Holdings, LLC, Common Equity11,420 — — — (5,317)6,103 — — Ridgeback Resources Inc., Common Equity41,851 — (35,240)(11,359)4,748 — — — Telpico, LLC, Common Equity— — — — — — — — $65,777 $139 $(35,746)$(11,359)$(2,561)$16,250 $157 $24  _____________ (1)    Gross additions may include increases in the cost basis of investments resulting from new portfolio investments, PIK interest, the amortization of unearned income, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company into this category from a different category. (2)    Gross reductions may include decreases in the cost basis of investments resulting from principal collections related to investment repayments or sales, the exchange of one or more existing securities for one or more new securities and/or the movement of an existing portfolio company out of this category into a different category. (3)    Interest and PIK income presented for the three months ended March 31, 2023.

[42] Security was on non-accrual status as of March 31, 2023.

[43] Investment denominated in Canadian dollars. Amortized cost and fair value are converted into U.S. dollars as of December 31, 2022.

[44] Investment denominated in Canadian dollars. Amortized cost and fair value are converted into U.S. dollars as of March 31, 2023.

[45] Includes the effect of swap contracts.

[46] Investment denominated in British pounds. Amortized cost and fair value are converted into U.S. dollars as of December 31, 2022.