Regulatory Assets and Liabilities and Regulatory Matters (Details) - USD ($) $ in Thousands				1 Months Ended	6 Months Ended	12 Months Ended
	Apr. 01, 2016	Jan. 19, 2016	Apr. 01, 2015	Mar. 31, 2016	Mar. 31, 2016	Sep. 30, 2014	Sep. 30, 2015	Mar. 31, 2015
Regulatory Assets
Capitalized project costs					$ 5,830
Project costs expensed in prior periods					5,734
Technology Equipment
Regulatory Assets
Capitalized project costs					2,755
Gas Utility
Regulatory Assets
Fair value of unrealized gains (losses)				$ (1,900)	(1,900)		$ (3,262)	$ (3,381)
Electric Utility
Regulatory Assets
Fair value of unrealized gains (losses)				$ (231)	(231)		$ (533)	$ (1,168)
Deferred Project Costs
Regulatory Assets
Capitalized project costs					$ 3,075
Pennsylvania Public Utility Commission
Regulatory Assets
Requested operating revenue increase		$ 58,600
Estimated time period for regulatory approval (in months)		9 months
Maximum period post petition to file general rate filing (in years)					5 years
Pennsylvania Public Utility Commission | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers				5.00%	5.00%	0.00%
PNG | Pennsylvania Public Utility Commission | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers			0.00%	10.00%
CPG | Pennsylvania Public Utility Commission | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers				10.00%
Subsequent Event | CPG | Pennsylvania Public Utility Commission | Maximum
Regulatory Assets
Distribution system improvement charge, percent of amount billed to customers	0.00%