CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
CURRENT ASSETS
Cash and cash equivalents	$ 103,421	$ 9,526
Customer and other receivables	245,884	299,904
Accrued unbilled revenues	88,907	96,796
Allowance for doubtful accounts	(2,504)	(3,203)
Materials and supplies (at average cost)	223,401	221,682
Fossil fuel (at average cost)	36,496	38,028
Deferred income taxes	58,630	91,152
Income tax receivable (Note 5)	4,647	135,517
Assets from risk management activities (Note 7)	16,951	17,169
Deferred fuel and purchased power regulatory asset (Note 3)		20,755
Other regulatory assets (Note 3)	76,317	76,388
Other current assets	45,780	39,895
Total current assets	897,930	1,043,609
INVESTMENTS AND OTHER ASSETS
Assets from risk management activities (Note 7)	21,626	23,815
Nuclear decommissioning trust (Note 13)	657,862	642,007
Other assets	60,753	60,875
Total investments and other assets	740,241	726,697
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	15,256,945	15,200,464
Accumulated depreciation and amortization	(5,360,781)	(5,300,219)
Net	9,896,164	9,900,245
Construction work in progress	646,236	581,369
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	124,157	125,125
Intangible assets, net of accumulated amortization	144,446	157,689
Nuclear fuel, net of accumulated amortization	144,048	124,557
Total property, plant and equipment	10,955,051	10,888,985
DEFERRED DEBITS
Regulatory assets (Note 3)	719,596	711,712
Other	137,979	137,683
Total deferred debits	857,575	849,395
TOTAL ASSETS	13,450,797	13,508,686
CURRENT LIABILITIES
Accounts payable	224,820	284,516
Accrued taxes (Note 5)	179,137	130,998
Accrued interest	47,392	48,351
Common dividends payable		62,528
Short-term borrowings (Note 2)	9,500	153,125
Current maturities of long-term debt (Note 2)	540,424	540,424
Customer deposits	75,999	76,101
Liabilities from risk management activities (Note 7)	19,907	31,892
Liabilities for asset retirements	25,536	32,896
Deferred fuel and purchased power regulatory liability (Note 3)	18,897
Other regulatory liabilities (Note 3)	116,903	99,273
Other current liabilities	136,128	158,540
Total current liabilities	1,394,643	1,618,644
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 2)	3,045,614	2,796,465
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,359,689	2,351,882
Regulatory liabilities (Note 3)	783,702	801,297
Liabilities for asset retirements	344,708	313,833
Liabilities for pension and other postretirement benefits (Note 4)	442,136	513,628
Liabilities from risk management activities (Note 7)	29,106	70,315
Customer advances	115,033	114,480
Coal mine reclamation	208,183	207,453
Deferred investment tax credit	152,114	152,361
Unrecognized tax benefits (Note 5)	13,502	42,209
Other	184,666	185,659
Total deferred credits and other	4,632,839	4,753,117
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
EQUITY (Note 8)
Common stock, no par value; authorized 150,000,000 shares, 110,389,065 and 110,280,703 issued at respective dates	2,497,485	2,491,558
Treasury stock at cost; 34,828 and 98,944 shares at respective dates	(844)	(4,308)
Total common stock	2,496,641	2,487,250
Retained earnings	1,801,047	1,785,273
Accumulated other comprehensive loss:
Pension and other postretirement benefits	(54,538)	(54,995)
Derivative instruments	(20,364)	(23,058)
Total accumulated other comprehensive loss	(74,902)	(78,053)
Total shareholders' equity	4,222,786	4,194,470
Noncontrolling interests (Note 6)	154,915	145,990
Total equity	4,377,701	4,340,460
TOTAL LIABILITIES AND EQUITY	$ 13,450,797	$ 13,508,686