Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Value Measurements, Recurring and Nonrecurring

Recurring fair value measurements by valuation hierarchy as of March 31, 2024 and December 31, 2023 are as follows:

			Fair Value Measurements Using
	Total as of		Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Other Observable Inputs		Significant Unobservable Inputs
Description	March 31, 2024		(Level 1)		(Level 2)		(Level 3)
	(in thousands)
Investment in CSI Compressco	$	12,204	$	12,204	$	—	$	—
Investment in CarbonFree	6,888		—		—		6,888
Investment in Standard Lithium	944		944		—		—
Other investments	350		—		—		350
Total investments	$	20,386

			Fair Value Measurements Using
	Total as of		Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Other Observable Inputs		Significant Unobservable Inputs
Description	December 31, 2023		(Level 1)		(Level 2)		(Level 3)
	(in thousands)
Investment in CSI Compressco	$	8,538	$	8,538	$	—	$	—
Investment in CarbonFree	6,850		—		—		6,850
Investment in Standard Lithium	1,616		1,616		—		—
Other investments	350		—		—		350
Investments	$	17,354

Investment

The change in our investments for the three-month periods ended March 31, 2024 and 2023 are as follows:

	Three Months Ended March 31, 2024
	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Unobservable Inputs
	(Level 1)		(Level 3)		Total
	(in thousands)
Investment balance at beginning of period	$	10,154	$	7,200	$	17,354
Unrealized gain on equity securities	2,994		—		2,994
Unrealized loss on embedded option	—		(199)		(199)
Unrealized gain on convertible note, excluding embedded option	—		237		237
Investment balance at end of period	$	13,148	$	7,238	$	20,386
	Three Months Ended March 31, 2023
	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets or Liabilities		Significant Unobservable Inputs
	(Level 1)		(Level 3)		Total
	(in thousands)
Investment balance at beginning of period	$	8,147	$	6,139	$	14,286
Unrealized loss on equity securities	(184)		—		(184)
Unrealized loss on embedded option	—		(321)		(321)
Unrealized gain on convertible note, excluding embedded option	—		121		121
Investment balance at end of period	$	7,963	$	5,939	$	13,902