Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

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 March 31, 2019 and December 31, 2018 by level within the fair value hierarchy (in thousands):

	March 31, 2019
	Level 1		Level 2		Level 3		Total
Money market funds	$	28,001	$	—	$	—	$	28,001
Common shares of CO2 Solutions	484		—		—		484
Total	$	28,485	$	—	$	—	$	28,485

	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