CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
CURRENT ASSETS
Cash and cash equivalents	$ 13,968	$ 9,969
Customer and other receivables	324,659	391,923
Accrued unbilled revenues	132,765	133,980
Allowance for doubtful accounts (Note 2)	(24,666)	(25,354)
Materials and supplies (at average cost)	358,287	349,135
Income tax receivable	6,972	7,514
Fossil fuel (at average cost)	20,772	18,032
Assets from risk management activities (Note 7)	206,102	63,481
Deferred fuel and purchased power regulatory asset (Note 4)	354,816	388,148
Other regulatory assets (Note 4)	131,444	130,376
Other current assets	69,474	83,896
Total current assets	1,594,593	1,551,100
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trusts (Notes 11 and 12)	1,227,465	1,294,757
Other special use funds (Notes 11 and 12)	349,042	358,410
Assets from risk management activities (Note 7)	91,521	46,908
Other assets	105,605	97,884
Total investments and other assets	1,773,633	1,797,959
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	21,844,618	21,688,661
Accumulated depreciation and amortization	(7,597,037)	(7,504,603)
Net	14,247,581	14,184,058
Construction work in progress	1,418,308	1,329,478
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	93,199	94,166
Intangible assets, net of accumulated amortization	269,802	273,693
Nuclear fuel, net of accumulated amortization	119,296	106,039
Total property, plant and equipment	16,148,186	15,987,434
DEFERRED DEBITS
Regulatory assets (Note 4)	1,184,246	1,192,987
Operating lease right-of-use assets	896,907	890,057
Assets for pension and other postretirement benefits (Note 5)	563,019	545,723
Other	40,370	37,962
Total deferred debits	2,684,542	2,666,729
TOTAL ASSETS	22,200,954	22,003,222
CURRENT LIABILITIES
Accounts payable	343,255	393,083
Accrued taxes	222,492	168,645
Accrued interest	61,648	57,332
Common dividends payable	0	95,988
Short-term borrowings (Note 3)	262,950	292,000
Current maturities of long-term debt (Note 3)	0	150,000
Customer deposits	41,628	42,293
Liabilities from risk management activities (Note 7)	1,706	4,373
Liabilities for asset retirements	4,069	4,473
Operating lease liabilities	100,949	100,443
Regulatory liabilities (Note 4)	448,778	296,271
Other current liabilities	109,255	151,968
Total current liabilities	1,596,730	1,756,869
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 3)	7,226,624	6,913,735
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,318,959	2,311,862
Regulatory liabilities (Note 4)	2,438,672	2,499,213
Liabilities for asset retirements	771,720	762,909
Liabilities for pension benefits (Note 5)	149,856	152,865
Customer advances	314,664	257,151
Coal mine reclamation	175,776	174,616
Deferred investment tax credit	186,251	186,570
Unrecognized tax benefits	4,758	4,657
Operating lease liabilities	735,718	728,401
Other	231,090	232,914
Total deferred credits and other	7,327,464	7,311,158
COMMITMENTS AND CONTINGENCIES (NOTE 8)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 113,047,699 and 113,014,528 issued at respective dates	2,706,325	2,702,743
Treasury stock at cost; 50,921 and 87,608 shares at respective dates	(3,648)	(6,401)
Total common stock	2,702,677	2,696,342
Retained earnings	3,281,601	3,264,719
Accumulated other comprehensive loss	(53,708)	(54,861)
Total shareholders’ equity	5,930,570	5,906,200
Noncontrolling interests (Note 6)	119,566	115,260
Total equity	6,050,136	6,021,460
TOTAL LIABILITIES AND EQUITY	$ 22,200,954	$ 22,003,222