Commitments and Contingencies (Commitments) (Details Textuals 2) (USD $)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Material tax assessments	$ 0
Industrial-source CO2 [Member]
Long-term Purchase Commitment [Line Items]
Term of long-term purchase commitments (years)	17 years
Oil price assumption for obligation estimate ($/Bbl)	60
Industrial-source CO2 [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase obligation of CO2	47,000,000
Industrial-source CO2 [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Aggregate purchase obligation of CO2	67,000,000
CO2 Volumetric production payments and industrial CO2 customers [Member]
Long-term Purchase Commitment [Line Items]
Significant supply commitment remaining volume committed (MMcf)	273,000
Term of long-term supply arrangement (years)	14 years
Significant supply commitment yearly maximum volume required (MMcf/d)	74
Helium Supply Arrangement [Member]
Long-term Purchase Commitment [Line Items]
Term of long-term supply arrangement (years)	20 years
Maximum annual payment in event of shortfall	8,000,000
Maximum payment in event of shortfall	$ 46,000,000