Cash equivalents and equity securities at December 31, 2018 and 2017 consisted of the following (in thousands):



	December 31, 2018
	Adjusted Cost		Gross Unrealized Gains ⁽³⁾		Gross Unrealized Losses (3)		Estimated Fair Value		Average Contractual Maturities
									(in days)
Money market funds ⁽¹⁾	$	31,225	$	—	$	—	$	31,225	n/a
Common shares of CO₂ Solutions ⁽²⁾	563		25		—		588		n/a
Total	$	31,788	$	25	$	—	$	31,813



	December 31, 2017
	Adjusted Cost		Gross Unrealized Gains (3)		Gross Unrealized Losses (3)		Estimated Fair Value		Average Contractual Maturities
									(in days)
Money market funds ⁽¹⁾	$	6,778	$	—	$	—	$	6,778	n/a
Common shares of CO₂ Solutions ⁽²⁾	563		108		—		671		n/a
Total	$	7,341	$	108	$	—	$	7,449

⁽¹⁾Money market funds are classified in cash and cash equivalents on our consolidated balance sheets.

⁽²⁾Common shares of CO₂ Solutions are classified in equity securities on our consolidated balance sheets.

⁽³⁾As a result of adopting ASU 2016-01, in 2018 and thereafter gross unrealized gains and gross unrealized losses related to our investment in CO₂ Solutions were recognized in other expense, in the consolidated statements of operations. Prior to 2018 gross unrealized gains and gross unrealized losses related to our investment in CO₂ Solutions were recorded in accumulated other comprehensive loss on the balance sheet.