Regulatory Assets and Liabilities and Regulatory Matters - Narrative (Details) - USD ($) $ in Thousands									1 Months Ended		3 Months Ended	9 Months Ended		12 Months Ended
	Jun. 30, 2018	May 17, 2018	Jan. 26, 2018	Oct. 20, 2017	Jul. 01, 2017	Oct. 19, 2016	Apr. 01, 2016	Apr. 01, 2015	Mar. 31, 2018	Mar. 31, 2016	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2014	Sep. 30, 2017
Regulatory Assets
PUC temporary rates order, reduction in revenue									$ 1,353		$ 22,745	$ 24,098	$ 0
Minimum
Regulatory Assets
Average remaining depreciable lives of associated property.												1 year
Maximum
Regulatory Assets
Average remaining depreciable lives of associated property.												65 years
PNG
Regulatory Assets
PUC temporary rates order, percent of reduction in base rate revenues		3.90%
UGI Gas
Regulatory Assets
PUC temporary rates order, percent of reduction in base rate revenues		5.78%
CPG
Regulatory Assets
PUC temporary rates order, percent of reduction in base rate revenues		8.19%
Pennsylvania Public Utilities Commission
Regulatory Assets
Requested operating revenue increase			$ 9,200
Pennsylvania PUC
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers												5.00%
Pennsylvania PUC | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers														0.00%
Pennsylvania PUC | PNG
Regulatory Assets
Increase in annual base distribution rate				$ 11,250
Distribution system improvement charge, percent of amount billed to customers					7.50%
Pennsylvania PUC | PNG | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers								0.00%
Pennsylvania PUC | UGI Gas
Regulatory Assets
Increase in annual base distribution rate						$ 27,000
Pennsylvania PUC | CPG
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers					7.50%
Pennsylvania PUC | CPG | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers							0.00%			10.00%
Pennsylvania PUC | Electric Utilities
Regulatory Assets
Requested operating revenue increase	$ 7,700
Gas Utility
Regulatory Assets
Fair value of unrealized gains (losses)	$ 1,863										$ 1,863	$ 1,863	$ (73)		$ 146