Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		3 Months Ended	9 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Environmental Issue [Member]	Jun. 30, 2013 Environmental Issue [Member] PNG MGP [Member]	Jun. 30, 2013 Environmental Remediation Expense [Member] CPG MGP [Member]	Jun. 30, 2013 Environmental Remediation Expense [Member] PNG MGP [Member]	Jun. 30, 2013 CPG and PNG COAs [Member]	Jun. 30, 2012 CPG and PNG COAs [Member]	Feb. 09, 2011 Allentown, Pennsylvania Natural Gas Explosion [Member] Damage from Natural Gas Explosion [Member] Persons
Commitments and Contingencies [Line Items]
Environmental expenditures cap during calendar year				$ 1,800	$ 1,100
Option to termination agreement by either party effective at end of any two-year period beginning with the original effective date in March 2004 (in years)			2 years
Accrual for environmental loss contingencies						14,399	15,820
Base year for determination of investigation and remediation cost (in years)		5 years
Deaths from natural gas explosion (in persons)								5
Liability insurance deductible	$ 500