Commitments (Details) (Long-term transportation contracts [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Remainder of 2012 through 2013 [Member] | Nytis LLC [Member]
Commitments (Textual)
Capacity levels (in dekatherms per day)	1,300
April 2013 through 2036 [Member] | Nytis LLC [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.22
Capacity levels (in dekatherms per day)	1,000
Maximum [Member] | Remainder of 2012 through 2013 [Member] | Nytis LLC [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.80
Minimum [Member] | Remainder of 2012 through 2013 [Member] | Nytis LLC [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.22
ING Assets acquisition [Member]
Commitments (Textual)
Liability related to firm transportation contracts assumed	5.4
ING Assets acquisition [Member] | Remainder of 2012 through 2013 [Member]
Commitments (Textual)
Capacity levels (in dekatherms per day)	7,700
ING Assets acquisition [Member] | 2014 through May 2015 [Member]
Commitments (Textual)
Capacity levels (in dekatherms per day)	3,450
ING Assets acquisition [Member] | June 2015 through 2017 [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.65
Capacity levels (in dekatherms per day)	2,300
ING Assets acquisition [Member] | Maximum [Member] | 2014 through May 2015 [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.65
ING Assets acquisition [Member] | Maximum [Member] | Remainder of 2012 through March 2013 [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	1.40
ING Assets acquisition [Member] | Minimum [Member] | 2014 through May 2015 [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.22
ING Assets acquisition [Member] | Minimum [Member] | Remainder of 2012 through March 2013 [Member]
Commitments (Textual)
Demand charges (in dollars per dekatherm)	0.22