Regulatory Matters (Narrative) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($)
Regulatory Matters [Line Items]
Amount of requested increase to annual revenues	$ 41.7
Recommended rate increase to annual revenues	$ 8.5
Recommended Equity Ratio	42.30%
Recommended Cost of Equity	8.60%
Approved Rate Increase	$ 5.9
Approved Cost of Equity	8.70%
Approved Equity Ratio	42.90%