Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]

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

The following table presents the financial instruments that were measured at fair value on a recurring basis at September 30, 2013 by level within the fair value hierarchy (in thousands):

	September 30, 2013
	Level 1		Level 2		Level 3		Total
Money market funds	$	21,079	$	—	$	—	$	21,079
Corporate bonds	—		1,007		—		1,007
U.S. Treasury obligations	—		2,002		—		2,002
Common shares of CO2 Solutions	—		1,067		—		1,067
Total	$	21,079	$	4,076	$	—	$	25,155

The following table presents the financial instruments that were measured at fair value on a recurring basis at December 31, 2012 by level within the fair value hierarchy (in thousands):

	December 31, 2012
	Level 1		Level 2		Level 3		Total
Money market funds	$	24,789	$	—	$	—	$	24,789
Commercial paper	—		1,500		—		1,500
Corporate bonds	—		9,522		—		9,522
U.S. Treasury obligations	—		5,515		—		5,515
Common shares of CO2 Solutions	610		—		—		610
Total	$	25,399	$	16,537	$	—	$	41,936