Commitments and Contingencies (Details Textuals 2) (USD $) In Millions, unless otherwise specified	12 Months Ended					12 Months Ended	3 Months Ended
	Dec. 31, 2012 Anthropogenic Co2 Contracts [Member]	Dec. 31, 2012 Anthropogenic Co2 Contracts [Member] Maximum [Member] MMcf	Dec. 31, 2012 Anthropogenic Co2 Contracts [Member] Minimum [Member] MMcf	Dec. 31, 2012 Volumetric production payments [Member] Y MMcf	Dec. 31, 2012 Volumetric production payments [Member] Maximum [Member] MMcf	Dec. 31, 2012 Riley Ridge [Member]	Dec. 31, 2012 Riley Ridge [Member] Helium Supply Arrangement [Member] Y
Long-term Purchase Commitment [Line Items]
Term of long-term purchase commitments	The commitments continue for up to 20 years.
Expected amount of CO2 to be delivered by third parties in future years (MMcf/d)		675	335
Aggregate purchase obligation of CO2		$ 190	$ 95
Oil price assumption for obligation estimate ($/Bbl)	100
Significant Supply Commitment Remaining Volume Committed					327,000
Term of Long Term Supply Arrangement (years)				14			20
Significant Supply Commitment Yearly Maximum Volume Required				109
Business Acquisition, Date of Acquisition Agreement						Aug. 01, 2011
Annual Payment In Event Of Shortfall							$ 8.0