CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating revenues	$ 1,012,786	$ 914,480
Purchased gas cost	371,163	288,260
Operation and maintenance expense	159,110	138,643
Depreciation and amortization expense	127,856	115,285
Taxes, other than income	78,796	73,452
Operating income	275,861	298,840
Other non-operating income	8,702	6,072
Interest charges	19,851	22,010
Income before income taxes	264,712	282,902
Income tax expense	15,503	65,224
Net income	$ 249,209	$ 217,678
Basic net income per share (USD per share)	$ 1.86	$ 1.71
Diluted net income per share (USD per share)	1.86	1.71
Cash dividends per share (USD per share)	$ 0.680	$ 0.625
Basic weighted average shares outstanding (in shares)	133,682	127,034
Diluted weighted average shares outstanding (in shares)	133,689	127,034
Other comprehensive income (loss), net of tax
Net unrealized holding losses on available-for-sale securities, net of tax of $20 and $18	$ (69)	$ (63)
Cash flow hedges:
Amortization and unrealized gain (loss) on interest rate agreements, net of tax of $(13,260) and $17,395	(45,878)	60,184
Total other comprehensive income (loss)	(45,947)	60,121
Total comprehensive income	203,262	277,799
Distribution segment
Operating revenues	971,636	875,887
Pipeline and storage segment
Operating revenues	41,150	38,593
Purchased gas cost
Purchased gas cost	371,163	288,260
Operating Segments | Distribution segment
Operating revenues	972,422	876,650
Purchased gas cost	496,799	411,072
Operation and maintenance expense	123,284	108,802
Depreciation and amortization expense	92,797	82,870
Taxes, other than income	69,045	64,352
Operating income	190,497	209,554
Other non-operating income	1,916	835
Interest charges	8,548	10,712
Income before income taxes	183,865	199,677
Income tax expense	4,294	45,985
Net income	179,571	153,692
Operating Segments | Pipeline and storage segment
Operating revenues	162,918	159,713
Purchased gas cost	(3,411)	(1,244)
Operation and maintenance expense	36,155	30,156
Depreciation and amortization expense	35,059	32,415
Taxes, other than income	9,751	9,100
Operating income	85,364	89,286
Other non-operating income	6,786	5,237
Interest charges	11,303	11,298
Income before income taxes	80,847	83,225
Income tax expense	11,209	19,239
Net income	69,638	63,986
Operating Segments | Purchased gas cost | Distribution segment
Purchased gas cost	496,799	411,072
Operating Segments | Purchased gas cost | Pipeline and storage segment
Purchased gas cost	(3,411)	(1,244)
Eliminations
Operating revenues	(122,554)	(121,883)
Purchased gas cost	(122,225)	(121,568)
Operation and maintenance expense	(329)	(315)
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
Eliminations | Distribution segment
Operating revenues	786	763
Eliminations | Pipeline and storage segment
Operating revenues	121,768	121,120
Eliminations | Purchased gas cost
Purchased gas cost	$ (122,225)	$ (121,568)