Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Value Measurements, Recurring and Nonrecurring

Recurring fair value measurements by valuation hierarchy as of June 30, 2023 and December 31, 2022 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	June 30, 2023		(Level 1)		(Level 2)		(Level 3)
	(in thousands)
Investment in CSI Compressco	$	6,599	$	6,599	$	—	$	—
Investment in CarbonFree	6,269		—		—		6,269
Investment in Standard Lithium	3,600		3,600		—		—
Other investment	250		—		—		250
Investments	$	16,718

			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, 2022		(Level 1)		(Level 2)		(Level 3)
	(in thousands)
Investment in CSI Compressco	$	6,967	$	6,967	$	—	$	—
Investment in CarbonFree	6,139		—		—		6,139
Investment in Standard Lithium	1,180		1,180		—		—
Investments	$	14,286

Investment

The change in our investment in CarbonFree for the six-month period ended June 30, 2023 is as follows:

	Six Months Ended June 30, 2023
	(in thousands)
Balance at beginning of period	$	6,139
Change in fair value of embedded option	(198)
Change in fair value of convertible note, excluding embedded option	328
Balance at end of period	$	6,269