CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
CURRENT ASSETS
Cash and cash equivalents	$ 79,479	$ 33,583
Customer and other receivables	365,309	284,183
Accrued unbilled revenues	136,425	125,239
Allowance for doubtful accounts	(4,297)	(3,748)
Materials and supplies (at average cost)	219,026	204,387
Fossil fuel (at average cost)	31,234	22,000
Deferred income taxes	95,487	130,571
Income tax receivable (Note 6)		6,466
Assets from risk management activities (Note 8)	26,257	30,264
Deferred fuel and purchased power regulatory asset (Note 3)	67,910	27,549
Other regulatory assets (Note 3)	53,960	69,072
Other current assets	28,062	26,904
Total current assets	1,098,852	956,470
INVESTMENTS AND OTHER ASSETS
Assets from risk management activities (Note 8)	38,449	49,322
Nuclear decommissioning trust (Note 15)	566,960	513,733
Other assets	62,428	64,588
Total investments and other assets	667,837	627,643
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	14,116,015	13,753,971
Accumulated depreciation and amortization	(4,901,833)	(4,709,991)
Net	9,214,182	9,043,980
Construction work in progress	587,826	496,745
Palo Verde sale leaseback, net of accumulated depreciation (Note 7)	129,962	132,864
Intangible assets, net of accumulated amortization	152,665	170,571
Nuclear fuel, net of accumulated amortization	139,873	118,098
Total property, plant and equipment	10,224,508	9,962,258
DEFERRED DEBITS
Regulatory assets (Note 3)	1,250,792	1,352,079
Income tax receivable (Note 6)	69,953	68,633
Other	148,344	143,935
Total deferred debits	1,469,089	1,564,647
TOTAL ASSETS	13,460,286	13,111,018
CURRENT LIABILITIES
Accounts payable	231,151	326,987
Accrued taxes (Note 6)	190,188	120,289
Accrued interest	50,890	54,872
Current maturities of long-term debt	90,360	477,435
Customer deposits	76,853	72,176
Liabilities from risk management activities (Note 8)	56,263	53,968
Regulatory liabilities (Note 3)	96,362	88,362
Other current liabilities	157,281	148,616
Total current liabilities	949,348	1,342,705
LONG-TERM DEBT LESS CURRENT MATURITIES
Long-term debt less current maturities	3,281,531	2,953,507
Palo Verde sale leaseback lessor notes less current maturities (Note 7)	57,420	65,547
Total long-term debt less current maturities	3,338,951	3,019,054
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,115,316	1,925,388
Regulatory liabilities (Note 3)	746,754	737,332
Liability for asset retirements	294,524	279,643
Liabilities for pension and other postretirement benefits (Note 4)	1,206,150	1,268,910
Liabilities from risk management activities (Note 8)	81,244	82,495
Customer advances	105,941	116,805
Coal mine reclamation	118,601	117,896
Unrecognized tax benefits (Note 6)	69,791	72,270
Other	248,082	217,934
Total deferred credits and other	4,986,403	4,818,673
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
EQUITY (Note 9)
Common stock, no par value	2,456,107	2,444,247
Treasury stock	(1,440)	(4,717)
Total common stock	2,454,667	2,439,530
Retained earnings	1,721,050	1,534,483
Accumulated other comprehensive loss:
Pension and other postretirement benefits	(62,695)	(65,447)
Derivative instruments	(56,780)	(86,716)
Total accumulated other comprehensive loss	(119,475)	(152,163)
Total shareholders' equity	4,056,242	3,821,850
Noncontrolling interests (Note 7)	129,342	108,736
Total equity	4,185,584	3,930,586
TOTAL LIABILITIES AND EQUITY	$ 13,460,286	$ 13,111,018