Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2016

Available-for-sale Securities [Abstract]

Schedule of cash equivalents and marketable securities

Cash equivalents and marketable securities at December 31, 2016 and 2015 consisted of the following (in thousands):

	December 31, 2016
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Average Contractual Maturities
									(in days)
Money market funds	$	11,172	$	—	$	—	$	11,172	n/a
Common shares of CO2 Solutions	563		579		—		1,142		n/a
Total	$	11,735	$	579	$	—	$	12,314

	December 31, 2015
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Average Contractual Maturities
									(in days)
Money market funds	$	11,120	$	—	$	—	$	11,120	n/a
Common shares of CO2 Solutions	563		986		—		1,549		n/a
Total	$	11,683	$	986	$	—	$	12,669