Disclosures About Derivative Instruments and Hedging Activities Textual (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Fair values of electric utility's forward purchase power agreements	$ 6,677	$ 39,959
Interest rate cash flow hedge loss to be reclassified during next 12 months, net	(2,680)
Restricted Cash in brokerage accounts	3,181	0
Electric Utility electric transmission congestion [Member]
Derivative [Line Items]
Notional amount (in units)	189,300,000	189,700,000
Gas Utility [Member]
Derivative [Line Items]
Notional amount (in units)	15,000,000	19,200,000
Maximum Length of Time Hedged in Price Risk Cash Flow Hedges	12 months
Electric Utility - Forward Contract [Member]
Derivative [Line Items]
Notional amount (in units)	245,800,000	570,400,000
Maximum Length of Time Hedged in Price Risk Cash Flow Hedges	8 months
Fair values of electric utility's forward purchase power agreements	4,759	9,207
Interest Rate Swap [Member]
Derivative [Line Items]
Underlying variable rate debt	0	173,000
Recorded loss amount included in Other Income, Net	$ (682)