Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Value Measurements, Recurring and Nonrecurring

Recurring fair value measurements by valuation hierarchy as of March 31, 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	March 31, 2023		(Level 1)		(Level 2)		(Level 3)
	(in thousands)
Investment in CSI Compressco	$	6,443	$	6,443	$	—	$	—
Investment in CarbonFree	5,939		—		—		5,939
Investment in Standard Lithium	1,520		1,520		—		—
Investments	$	13,902

			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 three-month period ended March 31, 2023 is as follows:

	Three Months Ended March 31, 2023
	(in thousands)
Balance at beginning of period	$	6,139
Change in fair value of embedded option	(321)
Change in fair value of convertible note, excluding embedded option	121
Balance at end of period	$	5,939