CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 500,826	$ 635,944	$ 570,052
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization including nuclear fuel	817,814	719,141	686,253
Deferred fuel and purchased power	(291,992)	(256,871)	(93,651)
Deferred fuel and purchased power amortization	219,579	44,557	(12,047)
Allowance for equity funds used during construction	(45,263)	(41,737)	(33,776)
Deferred income taxes	43,202	117,471	69,469
Deferred investment tax credit	(5,893)	(4,802)	(5,096)
Change in derivative instruments fair value	777	0	0
Stock compensation	15,942	18,460	18,292
Changes in current assets and liabilities:
Customer and other receivables	(63,869)	(72,559)	(18,191)
Accrued unbilled revenues	(30,784)	(1,783)	(4,032)
Materials, supplies and fossil fuel	(83,469)	(32,870)	11,623
Income tax receivable	(6,572)	(722)	14,935
Other current assets	76,067	(22,720)	(30,640)
Accounts payable	90,076	20,267	(6,059)
Accrued taxes	(4,205)	9,094	14,652
Other current liabilities	(6,056)	(52,086)	22,520
Change in margin and collateral accounts — assets	22	(50)	404
Change in margin and collateral accounts — liabilities	4,200	350	100
Change in unrecognized tax benefits	(1,989)	(568)	2,220
Change in long-term regulatory liabilities	(332,470)	57,549	13,017
Change in other long-term assets	276,821	(246,473)	(67,453)
Change in other long-term liabilities	68,677	(29,578)	(186,227)
Net cash provided by operating activities	1,241,441	860,014	966,365
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(1,707,490)	(1,473,475)	(1,326,584)
Contributions in aid of construction	137,436	105,654	62,503
Allowance for borrowed funds used during construction	(28,030)	(21,052)	(18,530)
Proceeds from nuclear decommissioning trust sales and other special use funds	1,207,713	1,720,966	819,518
Investment in nuclear decommissioning trust and other special use funds	(1,212,063)	(1,725,480)	(822,608)
Other	(15,612)	6,458	7,883
Net cash used for investing activities	(1,618,046)	(1,386,929)	(1,277,818)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	875,537	746,999	1,596,672
Repayment of long-term debt	(150,000)	0	(915,150)
Short-term borrowings and (repayments) — net	48,720	142,000	73,325
Short-term debt borrowings under revolving credit facility	0	0	751,690
Short-term debt repayments under revolving credit facility	0	(19,000)	(770,690)
Dividends paid on common stock	(378,881)	(369,478)	(350,577)
Common stock equity issuance and purchases — net	(2,653)	(2,350)	(1,389)
Distributions to noncontrolling interests	(21,255)	(21,255)	(22,743)
Net cash provided by financing activities	371,468	476,916	361,138
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(5,137)	(49,999)	49,685
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	9,969	59,968	10,283
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 4,832	$ 9,969	$ 59,968