Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2017

Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [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 June 30, 2017 and December 31, 2016 by level within the fair value hierarchy (in thousands):

	June 30, 2017
	Level 1		Level 2		Level 3		Total
Money market funds	$	10,736	$	—	$	—	$	10,736
Common shares of CO2 Solutions			1,305		—		1,305
Total	$	10,736	$	1,305	$	—	$	12,041

	December 31, 2016
	Level 1		Level 2		Level 3		Total
Money market funds	$	11,172	$	—	$	—	$	11,172
Common shares of CO2 Solutions	—		1,142		—		1,142
Total	$	11,172	$	1,142	$	—	$	12,314