CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
CURRENT ASSETS
Cash and cash equivalents	$ 27,803	$ 26,202
Customer and other receivables	345,581	277,225
Accrued unbilled revenues	163,608	94,845
Allowance for doubtful accounts	(2,821)	(3,340)
Materials and supplies (at average cost)	220,025	218,096
Fossil fuel (at average cost)	33,407	31,334
Deferred income taxes	105,146	152,191
Income tax receivable (Note 5)	2,317	2,423
Assets from risk management activities (Note 7)	22,575	25,699
Deferred fuel and purchased power regulatory asset (Note 3)	26,526	72,692
Other regulatory assets (Note 3)	79,405	71,257
Other current assets	42,717	37,102
Total current assets	1,066,289	1,005,726
INVESTMENTS AND OTHER ASSETS
Assets from risk management activities (Note 7)	31,918	35,891
Nuclear decommissioning trust (Note 13)	595,231	570,625
Other assets	64,304	62,694
Total investments and other assets	691,453	669,210
PROPERTY, PLANT AND EQUIPMENT
Plant in service and held for future use	14,503,810	14,346,367
Accumulated depreciation and amortization	(5,022,729)	(4,929,613)
Net	9,481,081	9,416,754
Construction work in progress	545,231	565,716
Palo Verde sale leaseback, net of accumulated depreciation (Note 6)	127,060	128,995
Intangible assets, net of accumulated amortization	162,715	162,150
Nuclear fuel, net of accumulated amortization	156,252	122,778
Total property, plant and equipment	10,472,339	10,396,393
DEFERRED DEBITS
Regulatory assets (Note 3)	1,120,366	1,099,900
Income tax receivable (Note 5)	71,274	70,389
Other	140,973	137,997
Total deferred debits	1,332,613	1,308,286
TOTAL ASSETS	13,562,694	13,379,615
CURRENT LIABILITIES
Accounts payable	287,368	221,312
Accrued taxes (Note 5)	129,865	124,939
Accrued interest	49,199	49,380
Common dividends payable	59,946	59,789
Short-term borrowings	30,100	92,175
Current maturities of long-term debt (Note 2)	599,131	122,828
Customer deposits	78,795	79,689
Liabilities from risk management activities (Note 7)	67,855	73,741
Regulatory liabilities (Note 3)	80,763	88,116
Other current liabilities	154,196	171,573
Total current liabilities	1,537,218	1,083,542
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 2)
Long-term debt less current maturities	2,782,758	3,160,219
Palo Verde sale leaseback lessor notes less current maturities (Note 6)	37,414	38,869
Total long-term debt less current maturities	2,820,172	3,199,088
DEFERRED CREDITS AND OTHER
Deferred income taxes	2,175,865	2,151,371
Regulatory liabilities (Note 3)	790,788	759,201
Liability for asset retirements	362,619	357,097
Liabilities for pension and other postretirement benefits (Note 4)	1,013,976	1,058,755
Deferred investment tax credit	119,979	99,819
Liabilities from risk management activities (Note 7)	85,474	85,264
Customer advances	108,335	109,359
Coal mine reclamation	115,145	118,860
Unrecognized tax benefits (Note 5)	72,629	71,135
Other	191,259	183,835
Total deferred credits and other	5,036,069	4,994,696
COMMITMENTS AND CONTINGENCIES (SEE NOTES)
EQUITY (Note 8)
Common stock, no par value	2,486,871	2,466,923
Treasury stock	(10,117)	(4,211)
Total common stock	2,476,754	2,462,712
Retained earnings	1,659,868	1,624,102
Accumulated other comprehensive loss:
Pension and other postretirement benefits	(64,138)	(64,416)
Derivative instruments	(40,319)	(49,592)
Total accumulated other comprehensive loss	(104,457)	(114,008)
Total shareholders' equity	4,032,165	3,972,806
Noncontrolling interests (Note 6)	137,070	129,483
Total equity	4,169,235	4,102,289
TOTAL LIABILITIES AND EQUITY	$ 13,562,694	$ 13,379,615