Consolidated Statements Of Operations And Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Consolidated Statements Of Operations [Abstract]
Operating revenues	$ 411,255	$ 434,618	$ 1,574,405	$ 1,582,649
Operating expenses:
Operations and maintenance	147,018	151,361	418,520	428,923
Purchased gas	16,590	52,041	314,838	354,896
Depreciation	84,348	80,471	252,208	235,774
Amortization	1,687	2,259	3,282	4,478
Taxes other than income taxes	24,207	22,625	67,433	67,352
Total operating expenses	273,850	308,757	1,056,281	1,091,423
Operating income	137,405	125,861	518,124	491,226
Other expense (income):
Interest expense	68,590	60,488	210,440	169,345
Interest income	(942)	(1,510)	(2,731)	(2,943)
Allowance for funds used during construction	(5,455)	(5,812)	(14,567)	(17,802)
Loss (gain) on sale of other assets	285	(299)	(184)	(777)
Other	(1,438)	(441)	(2,001)	(2,566)
Income before income taxes	76,365	73,435	327,167	345,969
Provision for income taxes (benefit)	(3,711)	4,797	(35,611)	(4,336)
Net income	80,076	68,638	362,778	350,305
Comprehensive income	$ 80,076	$ 68,638	$ 362,778	$ 350,305
Net income per common share:
Basic	$ 0.30	$ 0.26	$ 1.37	$ 1.34
Diluted	$ 0.30	$ 0.26	$ 1.37	$ 1.33
Average common shares outstanding during the period:
Basic	266,767	262,213	265,135	262,089
Diluted	267,176	262,754	265,688	262,641