Fair Value Measurements (Schedule of Financial Instruments Measured at Fair Value on Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	$ 15,315	$ 15,290
Level 1 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	14,603	14,602
Level 2 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	712	688
Level 3 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	0	0
Money market funds [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	14,603	14,602
Money market funds [Member] | Level 1 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	14,603	14,602
Money market funds [Member] | Level 2 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	0	0
Money market funds [Member] | Level 3 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	0	0
Common shares of CO2 Solution [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	712	688
Common shares of CO2 Solution [Member] | Level 1 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	0	0
Common shares of CO2 Solution [Member] | Level 2 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	712	688
Common shares of CO2 Solution [Member] | Level 3 [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	$ 0	$ 0