Fair Value Measurements (Schedule of Financial Instruments Measured at Fair Value on Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis	$ 15,631			$ 19,889
Assets held for sale	0	292	1,394	2,179
Assets Held-for-sale [Member]
Summary of financial instruments measured at fair value on a recurring basis
Assets held for sale				2,179
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	14,600			16,089
Level 1 [Member] | Assets Held-for-sale [Member]
Summary of financial instruments measured at fair value on a recurring basis
Assets held for sale				0
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	1,031			3,800
Level 2 [Member] | Assets Held-for-sale [Member]
Summary of financial instruments measured at fair value on a recurring basis
Assets held for sale				0
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
Level 3 [Member] | Assets Held-for-sale [Member]
Summary of financial instruments measured at fair value on a recurring basis
Assets held for sale				2,179
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	14,600			16,089
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	14,600			16,089
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
Corporate bonds [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis				1,005
Corporate bonds [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
Corporate bonds [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				1,005
Corporate bonds [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
U.S. Treasury obligations [Member]
Summary of financial instruments measured at fair value on a recurring basis
Total financial assets measured at fair value on a recurring basis				2,000
U.S. Treasury obligations [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
U.S. Treasury obligations [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				2,000
U.S. Treasury obligations [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
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	1,031			795
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	1,031			795
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