CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating revenues	$ 605,553	$ 492,995	$ 2,839,106	$ 2,346,223
Purchased gas cost	86,870	26,072	948,939	640,823
Operation and maintenance expense	184,470	149,460	479,488	449,529
Depreciation and amortization expense	119,348	107,104	353,269	318,082
Taxes, other than income	81,475	71,324	243,376	214,535
Operating income	133,390	139,035	814,034	723,254
Other non-operating income	5,887	7,235	14,793	9,133
Interest charges	20,962	19,580	69,068	68,980
Income before income taxes	118,315	126,690	759,759	663,407
Income tax expense	15,904	8,899	142,916	127,297
Net income	$ 102,411	$ 117,791	$ 616,843	$ 536,110
Basic net income per share (USD per share)	$ 0.78	$ 0.96	$ 4.77	$ 4.38
Diluted net income per share (USD per share)	0.78	0.96	4.77	4.37
Cash dividends per share (USD per share)	$ 0.625	$ 0.575	$ 1.875	$ 1.725
Basic weighted average shares outstanding (in shares)	131,358	123,026	129,185	122,352
Diluted weighted average shares outstanding (in shares)	131,486	123,032	129,229	122,463
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax of $(11) and $96	$ (36)	$ 364	$ (165)	$ 200
Cash flow hedges:
Amortization and unrealized loss on interest rate agreements, net of tax of $(22,890) and $(1,115)	(79,196)	(4,450)	118,993	(2,344)
Total other comprehensive income (loss)	(79,232)	(4,086)	118,828	(2,144)
Total comprehensive income	23,179	113,705	735,671	533,966
Distribution segment
Operating revenues	557,931	434,650	2,715,644	2,194,786
Pipeline and storage segment
Operating revenues	47,622	58,345	123,462	151,437
Operating Segments | Distribution segment
Operating revenues	558,750	435,308	2,718,074	2,196,817
Purchased gas cost	202,050	126,093	1,304,269	942,586
Operation and maintenance expense	130,454	107,537	363,246	337,740
Depreciation and amortization expense	86,099	77,187	254,636	229,526
Taxes, other than income	72,024	61,980	214,991	190,636
Operating income	68,123	62,511	580,932	496,329
Other non-operating income	1,060	5,167	1,135	1,930
Income before income taxes	60,643	59,709	548,798	463,131
Income tax expense	7,354	810	109,481	87,411
Net income	53,289	58,899	439,317	375,720
Operating Segments | Pipeline and storage segment
Operating revenues	162,987	158,008	476,868	452,421
Purchased gas cost	691	(11)	(440)	290
Operation and maintenance expense	54,329	42,234	117,188	112,751
Depreciation and amortization expense	33,249	29,917	98,633	88,556
Taxes, other than income	9,451	9,344	28,385	23,899
Operating income	65,267	76,524	233,102	226,925
Other non-operating income	4,827	2,068	13,658	7,203
Income before income taxes	57,672	66,981	210,961	200,276
Income tax expense	8,550	8,089	33,435	39,886
Net income	49,122	58,892	177,526	160,390
Eliminations
Operating revenues	(116,184)	(100,321)	(355,836)	(303,015)
Purchased gas cost	(115,871)	(100,010)	(354,890)	(302,053)
Operation and maintenance expense	(313)	(311)	(946)	(962)
Depreciation and amortization expense	0	0	0	0
Taxes, other than income	0	0	0	0
Operating income	0	0	0	0
Other non-operating income	0	0	0	0
Income before income taxes	0	0	0	0
Income tax expense	0	0	0	0
Net income	0	0	0	0
Eliminations | Distribution segment
Operating revenues	819	658	2,430	2,031
Eliminations | Pipeline and storage segment
Operating revenues	115,365	99,663	353,406	300,984
Purchased gas cost
Purchased gas cost	86,870	26,072	948,939	640,823
Purchased gas cost | Operating Segments | Distribution segment
Purchased gas cost	202,050	126,093	1,304,269	942,586
Purchased gas cost | Operating Segments | Pipeline and storage segment
Purchased gas cost	691	(11)	(440)	290
Purchased gas cost | Eliminations
Purchased gas cost	$ (115,871)	$ (100,010)	$ (354,890)	$ (302,053)