CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Operating revenues	$ 1,649,819	$ 1,319,073	$ 2,662,605	$ 2,233,553
Purchased gas cost	871,378	573,809	1,242,541	862,069
Operation and maintenance expense	163,352	156,375	322,462	295,018
Depreciation and amortization expense	133,374	118,636	261,230	233,921
Taxes, other than income	96,583	88,449	175,379	161,901
Operating income	385,132	381,804	660,993	680,644
Other non-operating income	5,213	2,834	13,915	8,906
Interest charges	28,928	26,096	48,779	48,106
Income before income taxes	361,417	358,542	626,129	641,444
Income tax expense	36,418	61,788	51,921	127,012
Net income	$ 324,999	$ 296,754	$ 574,208	$ 514,432
Basic net income per share (USD per share)	$ 2.37	$ 2.30	$ 4.24	$ 4.01
Diluted net income per share (USD per share)	2.37	2.30	4.24	4.01
Cash dividends per share (USD per share)	$ 0.68	$ 0.625	$ 1.36	$ 1.25
Basic weighted average shares outstanding (in shares)	136,834	129,161	135,259	128,098
Diluted weighted average shares outstanding (in shares)	137,250	129,164	135,470	128,100
Other comprehensive income (loss), net of tax
Net unrealized holding losses on available-for-sale securities	$ (161)	$ (66)	$ (230)	$ (129)
Cash flow hedges:
Amortization and unrealized gain on interest rate agreements	121,884	138,005	76,006	198,189
Total other comprehensive income	121,723	137,939	75,776	198,060
Total comprehensive income	446,722	434,693	649,984	712,492
Distribution segment
Operating revenues	1,609,667	1,281,826	2,581,303	2,157,713
Pipeline and storage segment
Operating revenues	40,152	37,247	81,302	75,840
Purchased gas cost
Purchased gas cost	871,378	573,809	1,242,541	862,069
Operating Segments | Distribution segment
Operating revenues	1,610,546	1,282,674	2,582,968	2,159,324
Purchased gas cost	993,854	691,147	1,490,653	1,102,219
Operation and maintenance expense	121,541	123,990	244,825	232,792
Depreciation and amortization expense	96,612	85,667	189,409	168,537
Taxes, other than income	87,236	78,615	156,281	142,967
Operating income	311,303	303,255	501,800	512,809
Other non-operating income	549	(760)	2,465	75
Interest charges	15,157	14,017	23,705	24,729
Income before income taxes	296,695	288,478	480,560	488,155
Income tax expense	27,844	56,142	32,138	102,127
Net income	268,851	232,336	448,422	386,028
Operating Segments | Pipeline and storage segment
Operating revenues	163,747	154,168	326,665	313,881
Purchased gas cost	1,683	113	(1,728)	(1,131)
Operation and maintenance expense	42,126	32,703	78,281	62,859
Depreciation and amortization expense	36,762	32,969	71,821	65,384
Taxes, other than income	9,347	9,834	19,098	18,934
Operating income	73,829	78,549	159,193	167,835
Other non-operating income	4,664	3,594	11,450	8,831
Interest charges	13,771	12,079	25,074	23,377
Income before income taxes	64,722	70,064	145,569	153,289
Income tax expense	8,574	5,646	19,783	24,885
Net income	56,148	64,418	125,786	128,404
Operating Segments | Purchased gas cost | Distribution segment
Purchased gas cost	993,854	691,147	1,490,653	1,102,219
Operating Segments | Purchased gas cost | Pipeline and storage segment
Purchased gas cost	1,683	113	(1,728)	(1,131)
Eliminations
Operating revenues	(124,474)	(117,769)	(247,028)	(239,652)
Purchased gas cost	(124,159)	(117,451)	(246,384)	(239,019)
Operation and maintenance expense	(315)	(318)	(644)	(633)
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
Interest charges	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	879	848	1,665	1,611
Eliminations | Pipeline and storage segment
Operating revenues	123,595	116,921	245,363	238,041
Eliminations | Purchased gas cost
Purchased gas cost	$ (124,159)	$ (117,451)	$ (246,384)	$ (239,019)