Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Summary of financial instruments measured at fair value on a recurring basis

The following tables present the financial instruments that were measured at fair value on a recurring basis at December 31, 2018 and 2017 by level within the fair value hierarchy (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Money market funds	$	31,225	$	—	$	—	$	31,225
Common shares of CO2 Solutions	588		—		—		588
Total	$	31,813	$	—	$	—	$	31,813

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Money market funds	$	6,778	$	—	$	—	$	6,778
Common shares of CO2 Solutions	—		671		—		671
Total	$	6,778	$	671	$	—	$	7,449