Fair Value Measurements - Market Risks and Derivative Hedge Contracts (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Total investments	$ 20,427	$ 17,354
Kodiak
Derivatives, Fair Value [Line Items]
Total investments	12,279
CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	6,798
Standard Lithium
Derivatives, Fair Value [Line Items]
Total investments	1,000
Other Investments
Derivatives, Fair Value [Line Items]
Total investments	350
(Level 1) | Kodiak
Derivatives, Fair Value [Line Items]
Total investments	12,279
(Level 1) | CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments		8,538
(Level 1) | CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 1) | Standard Lithium
Derivatives, Fair Value [Line Items]
Total investments	1,000	1,616
(Level 1) | Other Investments
Derivatives, Fair Value [Line Items]
Total investments	0	0
(Level 2) | Kodiak
Derivatives, Fair Value [Line Items]
Total investments	0
(Level 2) | CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments		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	0
(Level 3) | Kodiak
Derivatives, Fair Value [Line Items]
Total investments	0
(Level 3) | CSI Compressco
Derivatives, Fair Value [Line Items]
Total investments		0
(Level 3) | CarbonFree
Derivatives, Fair Value [Line Items]
Total investments	6,798	6,850
(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	$ 350