CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
CURRENT ASSETS
Cash and cash equivalents	$ 9,969	$ 59,968
Customer and other receivables	391,923	313,576
Accrued unbilled revenues	133,980	132,197
Allowance for doubtful accounts (Note 2)	(25,354)	(19,782)
Materials and supplies (at average cost)	349,135	314,745
Fossil fuel (at average cost)	18,032	19,552
Income tax receivable (Note 5)	7,514	6,792
Assets from risk management activities (Note 16)	63,481	2,931
Deferred fuel and purchased power regulatory asset (Note 4)	388,148	175,835
Other regulatory assets (Note 4)	130,376	115,878
Other current assets	83,896	76,627
Total current assets	1,551,100	1,198,319
INVESTMENTS AND OTHER ASSETS
Nuclear decommissioning trust (Notes 13 and 19)	1,294,757	1,138,435
Other special use funds (Notes 13 and 19)	358,410	254,509
Assets from risk management activities (Note 16)	46,908	1,818
Other assets	97,884	91,104
Total investments and other assets	1,797,959	1,485,866
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 7 and 10)
Plant in service and held for future use	21,688,661	20,837,885
Accumulated depreciation and amortization	(7,504,603)	(7,110,310)
Net	14,184,058	13,727,575
Construction work in progress	1,329,478	937,384
Palo Verde sale leaseback, net of accumulated depreciation	94,166	98,036
Intangible assets, net of accumulated amortization	273,693	282,570
Nuclear fuel, net of accumulated amortization	106,039	113,645
Total property, plant and equipment	15,987,434	15,159,210
DEFERRED DEBITS
Regulatory assets (Notes 1, 4 and 5)	1,192,987	1,133,987
Operating lease right-of-use assets (Note 9)	890,057	505,064
Assets for pension and other postretirement benefits (Note 8)	545,723	502,992
Other	37,962	34,983
Total deferred debits	2,666,729	2,177,026
Total Assets	22,003,222	20,020,421
CURRENT LIABILITIES
Accounts payable	393,083	318,585
Accrued taxes	168,645	159,551
Accrued interest	57,332	56,962
Common dividends payable	95,988	93,531
Short-term borrowings (Note 6)	292,000	169,000
Current maturities of long-term debt (Note 7)	150,000	0
Customer deposits	42,293	48,340
Liabilities from risk management activities (Note 16)	4,373	7,557
Liabilities for asset retirements (Note 12)	4,473	15,586
Operating lease liabilities (Note 9)	100,443	74,785
Regulatory liabilities (Note 4)	296,271	229,088
Other current liabilities	151,968	187,448
Total current liabilities	1,756,869	1,360,433
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 7)	6,913,735	6,314,266
DEFERRED CREDITS AND OTHER
Deferred income taxes (Note 5)	2,311,862	2,135,403
Regulatory liabilities (Notes 1, 4, 5 and 8)	2,499,213	2,450,169
Liabilities for asset retirements (Note 12)	762,909	689,497
Liabilities for pension benefits (Note 8)	152,865	166,484
Liabilities from risk management activities (Note 16)	0	11,062
Customer advances	257,151	221,032
Coal mine reclamation	174,616	170,097
Deferred investment tax credit	186,570	191,372
Unrecognized tax benefits (Note 5)	4,657	5,834
Operating lease liabilities (Note 9)	728,401	361,336
Other	232,914	190,643
Total deferred credits and other	7,311,158	6,592,929
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
EQUITY
Common stock, no par value; authorized 150,000,000 shares, 113,014,528 and 112,760,051 issued at respective dates	2,702,743	2,677,482
Treasury stock at cost; 87,608 shares at end of 2021 and 72,006 shares at end of 2020	(6,401)	(6,289)
Total common stock	2,696,342	2,671,193
Retained earnings	3,264,719	3,025,106
Accumulated other comprehensive loss	(54,861)	(62,796)
Total shareholders’ equity	5,906,200	5,633,503
Noncontrolling interests (Note 18)	115,260	119,290
Total equity	6,021,460	5,752,793
Total Liabilities and Equity	$ 22,003,222	$ 20,020,421