CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
OPERATING REVENUES (Note 2)	$ 1,308,994	$ 1,121,703	$ 2,260,706	$ 2,066,658
OPERATING EXPENSES
Fuel and purchased power	437,172	407,754	795,036	802,258
Operations and maintenance	272,266	277,238	529,844	527,318
Depreciation and amortization	225,017	195,101	435,311	387,007
Taxes other than income taxes	58,651	57,642	117,815	114,780
Other expense	2,141	688	2,161	1,298
Total	995,247	938,423	1,880,167	1,832,661
OPERATING INCOME	313,747	183,280	380,539	233,997
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	8,910	13,034	19,202	28,095
Pension and other postretirement non-service credits - net (Note 5)	12,877	10,474	24,445	20,339
Other income (Note 9)	5,885	6,406	36,492	12,483
Other expense (Note 9)	(3,032)	(4,813)	(10,599)	(8,944)
Total	24,640	25,101	69,540	51,973
INTEREST EXPENSE
Interest charges	108,891	93,832	208,665	181,951
Allowance for borrowed funds used during construction	(11,036)	(12,317)	(24,177)	(25,039)
Total	97,855	81,515	184,488	156,912
Income Before Income Taxes	240,532	126,866	265,591	129,058
Income Taxes	32,421	15,897	36,312	17,080
Net Income	208,111	110,969	229,279	111,978
Less: Net income attributable to noncontrolling interests (Note 6)	4,306	4,306	8,612	8,612
Net Income Attributable to Common Shareholders	$ 203,805	$ 106,663	$ 220,667	$ 103,366
Weighted-average common shares outstanding - basic (in shares)	113,695	113,411	113,658	113,385
Weighted-average common shares outstanding - diluted (in shares)	115,803	113,717	115,015	113,657
Earnings Per Weighted-Average Common Share Outstanding
Net income attributable to common shareholders - basic (in dollars per share)	$ 1.79	$ 0.94	$ 1.94	$ 0.91
Net income attributable to common shareholders - diluted (in dollars per share)	$ 1.76	$ 0.94	$ 1.92	$ 0.91