Fair Value Measurements - Market Risks and Derivative Hedge Contracts (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Total investments	$ 16,405	$ 14,286
CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments	7,228	6,967
CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	6,563	6,139
Standard Lithium
Derivatives, Fair Value [Line Items]
Total investments	2,264	1,180
Other Investments
Derivatives, Fair Value [Line Items]
Total investments	350
(Level 1) | CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments	7,228	6,967
(Level 1) | CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 1) | Standard Lithium
Derivatives, Fair Value [Line Items]
Total investments	2,264	1,180
(Level 1) | Other Investments
Derivatives, Fair Value [Line Items]
Total investments	0
(Level 2) | CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 2) | CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 2) | Standard Lithium
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 2) | Other Investments
Derivatives, Fair Value [Line Items]
Total investments	0
(Level 3) | CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 3) | CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	6,563	6,139
(Level 3) | Standard Lithium
Derivatives, Fair Value [Line Items]
Total investments	0	$ 0
(Level 3) | Other Investments
Derivatives, Fair Value [Line Items]
Total investments	$ 350