Significant Accounting Policies Textuals (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Accounting Policies [Abstract]
Other Comprehensive Income (Loss), Net of Tax	$ (7,984)	$ (10,473)	$ 71,690
Reclassification of benefit plans actuarial losses and prior service costs net of tax to regulatory assets			$ 83,302
Gas Utility [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense as percentage of related average depreciable base	2.20%	2.30%	2.30%
Electric Utility [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense as percentage of related average depreciable base	2.40%	2.60%	2.60%