Segment Information (Tables)

6 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Schedule of Segment Information

				Reportable Segments
Three Months Ended March 31, 2019	Total			Gas Utility			Electric Utility
Revenues	$	429,592		$	401,415		$	28,177
Cost of sales	$	217,976		$	202,164		$	15,812
Depreciation	$	22,341		$	20,902		$	1,439
Operating income	$	119,866		$	116,580		$	3,286
Pension and other postretirement plans non-service income	$	395		$	346		$	49
Interest expense	$	(12,231	)	$	(11,622	)	$	(609	)
Income before income taxes	$	108,030		$	105,304		$	2,726
Capital expenditures (including the effects of accruals)	$	70,799		$	66,766		$	4,033

				Reportable Segments
Three Months Ended March 31, 2018	Total			Gas Utility			Electric Utility
Revenues	$	483,261		$	455,973		$	27,288
Cost of sales	$	257,302		$	241,031		$	16,271
Depreciation	$	21,158		$	19,776		$	1,382
Operating income (a)	$	135,771		$	134,738		$	1,033
Pension and other postretirement plans non-service expense (a)	$	(644	)	$	(563	)	$	(81	)
Interest expense	$	(11,091	)	$	(10,866	)	$	(225	)
Income before income taxes	$	124,036		$	123,309		$	727
Capital expenditures (including the effects of accruals)	$	55,089		$	51,363		$	3,726

				Reportable Segments
Six Months Ended March 31, 2019	Total			Gas Utility			Electric Utility
Revenues	$	752,317		$	698,557		$	53,760
Cost of sales	$	377,495		$	347,284		$	30,211
Depreciation	$	44,815		$	41,942		$	2,873
Operating income	$	196,940		$	190,164		$	6,776
Pension and other postretirement plans non-service income	$	807		$	707		$	100
Interest expense	$	(23,969	)	$	(22,840	)	$	(1,129	)
Income before income taxes	$	173,778		$	168,031		$	5,747
Capital expenditures (including the effects of accruals)	$	148,118		$	141,840		$	6,278
As of March 31, 2019
Total assets	$	3,438,437		$	3,252,092		$	186,345
Goodwill	$	182,145		$	182,145		$	—

				Reportable Segments
Six Months Ended March 31, 2018	Total			Gas Utility			Electric Utility
Revenues	$	806,366		$	755,938		$	50,428
Cost of sales	$	409,076		$	379,889		$	29,187
Depreciation	$	41,512		$	38,776		$	2,736
Operating income (a)	$	232,641		$	228,923		$	3,718
Pension and other postretirement plans non-service expense (a)	$	(1,219	)	$	(1,067	)	$	(152	)
Interest expense	$	(22,030	)	$	(21,392	)	$	(638	)
Income before income taxes	$	209,392		$	206,464		$	2,928
Capital expenditures (including the effects of accruals)	$	126,788		$	120,205		$	6,583
As of March 31, 2018
Total assets	$	3,204,045		$	3,033,352		$	170,693
Goodwill	$	182,145		$	182,145		$	—