CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
CURRENT ASSETS
Cash and cash equivalents	$ 20,710	$ 33,583
Customer and other receivables	238,387	284,183
Accrued unbilled revenues	104,728	125,239
Allowance for doubtful accounts	(2,886)	(3,748)
Materials and supplies (at average cost)	213,290	204,387
Fossil fuel (at average cost)	26,850	22,000
Deferred income taxes	141,224	130,571
Income tax receivable (Note 6)	8,894	6,466
Assets from risk management activities (Note 8)	34,617	30,264
Deferred fuel and purchased power regulatory asset (Note 3)	5,310	27,549
Other regulatory assets (Note 3)	81,457	69,072
Other current assets	32,219	26,904
Total current assets	904,800	956,470
INVESTMENTS AND OTHER ASSETS
Assets from risk management activities (Note 8)	53,124	49,322
Nuclear decommissioning trust (Note 15)	541,989	513,733
Other assets	64,415	64,588
Total investments and other assets	659,528	627,643
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	13,928,709	13,753,971
Accumulated depreciation and amortization	(4,775,904)	(4,709,991)
Net	9,152,805	9,043,980
Construction work in progress	462,425	496,745
Palo Verde sale leaseback, net of accumulated depreciation (Note 7)	131,897	132,864
Intangible assets, net of accumulated amortization	170,198	170,571
Nuclear fuel, net of accumulated amortization	141,882	118,098
Total property, plant and equipment	10,059,207	9,962,258
DEFERRED DEBITS
Regulatory assets (Note 3)	1,344,523	1,352,079
Income tax receivable (Note 6)	69,069	68,633
Other	146,787	143,935
Total deferred debits	1,560,379	1,564,647
TOTAL ASSETS	13,183,914	13,111,018
CURRENT LIABILITIES
Accounts payable	265,975	326,987
Accrued taxes (Note 6)	160,136	120,289
Accrued interest	44,736	54,872
Short-term borrowings	216,600
Current maturities of long-term debt	101,708	477,435
Customer deposits	74,297	72,176
Liabilities from risk management activities (Note 8)	89,207	53,968
Regulatory liabilities (Note 3)	89,622	88,362
Other current liabilities	115,618	148,616
Total current liabilities	1,157,899	1,342,705
LONG-TERM DEBT LESS CURRENT MATURITIES
Long-term debt less current maturities	3,275,651	2,953,507
Palo Verde sale leaseback lessor notes less current maturities (Note 7)	65,547	65,547
Total long-term debt less current maturities	3,341,198	3,019,054
DEFERRED CREDITS AND OTHER
Deferred income taxes	1,918,995	1,925,388
Regulatory liabilities (Note 3)	754,210	737,332
Liability for asset retirements	284,839	279,643
Liabilities for pension and other postretirement benefits (Note 4)	1,277,227	1,268,910
Liabilities from risk management activities (Note 8)	64,168	82,495
Customer advances	113,514	116,805
Coal mine reclamation	118,113	117,896
Unrecognized tax benefits (Note 6)	72,622	72,270
Other	219,700	217,934
Total deferred credits and other	4,823,388	4,818,673
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
EQUITY (Note 9)
Common stock, no par value	2,450,296	2,444,247
Treasury stock	(6,471)	(4,717)
Total common stock	2,443,825	2,439,530
Retained earnings	1,468,869	1,534,483
Accumulated other comprehensive loss:
Pension and other postretirement benefits	(64,481)	(65,447)
Derivative instruments	(103,296)	(86,716)
Total accumulated other comprehensive loss	(167,777)	(152,163)
Total shareholders' equity	3,744,917	3,821,850
Noncontrolling interests (Note 7)	116,512	108,736
Total equity	3,861,429	3,930,586
TOTAL LIABILITIES AND EQUITY	$ 13,183,914	$ 13,111,018