Segment Information (Tables)

3 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Schedule of Segment Information

				Reportable Segments
Three Months Ended December 31, 2018	Total			Gas Utility			Electric Utility
Revenues	$	322,725		$	297,142		$	25,583
Cost of sales	$	159,519		$	145,120		$	14,399
Depreciation	$	22,474		$	21,040		$	1,434
Operating income	$	77,074		$	73,584		$	3,490
Pension and other postretirement plans non-service income	$	412		$	361		$	51
Interest expense	$	(11,738	)	$	(11,218	)	$	(520	)
Income before income taxes	$	65,748		$	62,727		$	3,021
Capital expenditures (including the effects of accruals)	$	77,319		$	75,074		$	2,245
As of December 31, 2018
Total assets	$	3,424,773		$	3,251,331		$	173,442
Goodwill	$	182,145		$	182,145		$	—

				Reportable Segments
Three Months Ended December 31, 2017	Total			Gas Utility			Electric Utility
Revenues	$	323,105		$	299,965		$	23,140
Cost of sales	$	151,774		$	138,858		$	12,916
Depreciation	$	20,354		$	19,000		$	1,354
Operating income (a)	$	96,870		$	94,185		$	2,685
Pension and other postretirement plans non-service expense (a)	$	(575	)	$	(504	)	$	(71	)
Interest expense	$	(10,939	)	$	(10,526	)	$	(413	)
Income before income taxes	$	85,356		$	83,155		$	2,201
Capital expenditures (including the effects of accruals)	$	71,699		$	68,842		$	2,857
As of December 31, 2017
Total assets	$	3,174,693		$	3,038,250		$	136,443
Goodwill	$	182,145		$	182,145		$	—