CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Operating revenues	$ 1,175,999	$ 1,158,467
Purchased gas cost	234,048	338,869
Operation and maintenance expense	207,044	166,345
Depreciation and amortization expense	180,533	164,608
Taxes, other than income	94,894	89,540
Operating income	459,480	399,105
Other non-operating income	24,634	17,886
Interest charges	52,925	51,875
Income before income taxes	431,189	365,116
Income tax expense	79,331	53,824
Net income	$ 351,858	$ 311,292
Basic net income per share (USD per share)	$ 2.25	$ 2.08
Diluted net income per share (USD per share)	2.23	2.08
Cash dividends per share (USD per share)	$ 0.870	$ 0.805
Basic weighted average shares outstanding (in shares)	156,301	149,796
Diluted weighted average shares outstanding (in shares)	157,824	149,796
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax of $(42) and $86	$ (138)	$ 296
Cash flow hedges:
Amortization and unrealized gains (losses) on interest rate agreements, net of tax of $3,492 and $(14,519)	16,561	(50,232)
Total other comprehensive income (loss)	16,423	(49,936)
Total comprehensive income	368,281	261,356
Distribution segment
Operating revenues	1,108,569	1,104,619
Pipeline and storage segment
Operating revenues	67,430	53,848
Operating Segments | Distribution segment
Operating revenues	1,109,335	1,105,338
Purchased gas cost	422,570	496,662
Operation and maintenance expense	154,514	127,615
Depreciation and amortization expense	133,627	119,685
Taxes, other than income	82,576	80,895
Operating income	316,048	280,481
Other non-operating income	10,084	5,839
Interest charges	34,249	34,581
Income before income taxes	291,883	251,739
Income tax expense	51,670	30,302
Net income	240,213	221,437
Operating Segments | Pipeline and storage segment
Operating revenues	255,390	211,169
Purchased gas cost	(58)	4
Operation and maintenance expense	52,792	38,973
Depreciation and amortization expense	46,906	44,923
Taxes, other than income	12,318	8,645
Operating income	143,432	118,624
Other non-operating income	14,550	12,047
Interest charges	18,676	17,294
Income before income taxes	139,306	113,377
Income tax expense	27,661	23,522
Net income	111,645	89,855
Intersegment eliminations
Operating revenues	(188,726)	(158,040)
Purchased gas cost	(188,464)	(157,797)
Operation and maintenance expense	(262)	(243)
Depreciation and amortization expense	0	0
Taxes, other than income	0	0
Operating income	0	0
Other non-operating income	0	0
Interest charges	0	0
Income before income taxes	0	0
Income tax expense	0	0
Net income	0	0
Intersegment eliminations | Distribution segment
Operating revenues	(766)	(719)
Intersegment eliminations | Pipeline and storage segment
Operating revenues	$ (187,960)	$ (157,321)