Commitments (Details) (Long-term transportation contracts [Member])	9 Months Ended
	Sep. 30, 2014 Dekatherm
Oct 2014 [Member]
Supply Commitment [Line Items]
Capacity levels (Dekatherms per day)	6,450
Nov 2014 - May 2015 [Member]
Supply Commitment [Line Items]
Capacity levels (Dekatherms per day)	4,450
Jun 2015 - Dec 2017 [Member]
Supply Commitment [Line Items]
Capacity levels (Dekatherms per day)	3,300
Jan 2018 - May 2036 [Member]
Supply Commitment [Line Items]
Capacity levels (Dekatherms per day)	1,000
Demand charges (in dollars per dekatherm)	0.22
Maximum [Member] | Oct 2014 [Member]
Supply Commitment [Line Items]
Demand charges (in dollars per dekatherm)	0.67
Maximum [Member] | Nov 2014 - May 2015 [Member]
Supply Commitment [Line Items]
Demand charges (in dollars per dekatherm)	0.67
Maximum [Member] | Jun 2015 - Dec 2017 [Member]
Supply Commitment [Line Items]
Demand charges (in dollars per dekatherm)	0.67
Minimum [Member] | Oct 2014 [Member]
Supply Commitment [Line Items]
Demand charges (in dollars per dekatherm)	0.20
Minimum [Member] | Nov 2014 - May 2015 [Member]
Supply Commitment [Line Items]
Demand charges (in dollars per dekatherm)	0.20
Minimum [Member] | Jun 2015 - Dec 2017 [Member]
Supply Commitment [Line Items]
Demand charges (in dollars per dekatherm)	0.22