Commitments and Contingencies (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commitments And Contingencies (Textual) [Abstract]
Minimum annual obligations under non-cancelable operating lease commitments for 2012	$ 6.2
Minimum annual obligations under non-cancelable operating lease commitments for 2013	5.9
Minimum annual obligations under non-cancelable operating lease commitments for 2014	5.8
Minimum annual obligations under non-cancelable operating lease commitments for 2015	1.0
Minimum annual obligations under non-cancelable operating lease commitments in total	18.8
Office space lease	10 years
Lease Expiration Period	2015
Lease renewable periods	two five-year
Minimum obligations of remaining gas transportation and processing due in year 2012	5.6
Minimum obligations of remaining gas transportation and processing due in year 2013	8.1
Minimum obligations of remaining gas transportation and processing due in year 2014	8.3
Minimum obligations of remaining gas transportation and processing due in year 2015	5.7
Minimum obligations of remaining gas transportation and processing due in year 2016	4.3
Minimum obligations of remaining gas transportation and processing total	32.0
Rental and lease expenses [Member]
Component of Operating Other Cost and Expense [Line Items]
Operating leases rent expense net included in general and administrative net	5.6	5.4	4.2
Operating leases rent expense net included in lease operating cost	13.9	10.5	10.5
Drilling and Completion Services [Member]
Component of Operating Other Cost and Expense [Line Items]
Commitments for services and materials	$ 59.7