Condensed Consolidated Statements of Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenues	$ 197,982	$ 287,306
Costs and expenses:
Cost of sales — gas, fuel and purchased power (excluding depreciation shown below)	75,439	143,052
Operating and administrative expenses	48,027	46,548
Operating and administrative expenses — related parties	2,180	2,782
Taxes other than income taxes	3,769	4,104
Depreciation	15,827	14,558
Amortization	874	867
Other operating loss (income), net	3,570	(245)
Total costs and expenses	149,686	211,666
Operating income	48,296	75,640
Interest expense	9,494	10,649
Income before income taxes	38,802	64,991
Income taxes	15,451	26,152
Net income	$ 23,351	$ 38,839