Financial Instruments Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Interest rate agreements fair value		$ (1,332)	$ 91,127	[1]
Forward commodity contracts fair value	[2]	0	9,847	[1]
Interest rate agreements		377	87	[1]
Forward commodity contracts	[2]	0	(4,865)	[1]
Total other comprehensive income (loss) from hedging, net of tax		$ (955)	$ 96,196	[1]
Regulated Segments Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate			37.00%
Nonregulated Segment Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate		39.00%	39.00%
Expected Earnings [Line Items]
Expected Recognition in Earnings of Deferred Gain (Losses), Interest Rate Agreements		$ (40,756)
Next Twelve Months [Member]
Expected Earnings [Line Items]
Expected Recognition in Earnings of Deferred Gain (Losses), Interest Rate Agreements		(1,508)
Thereafter [Member]
Expected Earnings [Line Items]
Expected Recognition in Earnings of Deferred Gain (Losses), Interest Rate Agreements		$ (39,248)

[1] Utilizing an income tax rate ranging from 37 percent to 39 percent based on the effective rates in each taxing jurisdiction for the three-month period ended December 31, 2016.

[2] Due to the sale of AEM, these amounts are included in income from discontinued operations