CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 407,152	$ 382,493
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization including nuclear fuel	377,971	360,570
Deferred fuel and purchased power	13,093	51,533
Deferred fuel and purchased power amortization	23,158	(91,894)
Allowance for equity funds used during construction	(18,698)	(15,639)
Deferred income taxes	256,132	197,527
Deferred investment tax credit	16,164	8,974
Change in derivative instruments fair value	537	(943)
Changes in current assets and liabilities:
Customer and other receivables	(178,029)	(76,697)
Accrued unbilled revenues	(37,710)	(11,186)
Materials, supplies and fossil fuel	(8,914)	(23,873)
Income tax receivable	(131,128)	6,466
Other current assets	(12,246)	(10,035)
Accounts payable	44,704	(69,776)
Accrued taxes	58,919	69,899
Other current liabilities	4,096	17,071
Change in margin and collateral accounts - assets	(327)	1,980
Change in long-term income tax receivable	137,270	(1,320)
Change in unrecognized tax benefits	(57,585)	(3,554)
Change in other long-term assets	(24,345)	(13,885)
Change in other long-term liabilities	(2,884)	37,181
Change in margin and collateral accounts - liabilities	15,000	114,579
Net cash flow provided by operating activities	882,330	929,471
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(581,515)	(670,684)
Contributions in aid of construction	34,910	41,451
Allowance for borrowed funds used during construction	(10,861)	(10,428)
Proceeds from nuclear decommissioning trust sales	363,944	295,126
Investment in nuclear decommissioning trust	(376,881)	(308,063)
Other	(1,553)	(520)
Net cash flow used for investing activities	(571,956)	(653,118)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	136,307	351,081
Repayment of long-term debt	(72,777)	(421,703)
Short-term borrowings and payments - net	(92,175)
Dividends paid on common stock	(174,485)	(167,074)
Common stock equity issuance	10,396	9,684
Distributions to noncontrolling interests	(9,197)	(2,630)
Other	812	185
Net cash flow used for financing activities	(201,119)	(230,457)
NET INCREASE IN CASH AND CASH EQUIVALENTS	109,255	45,896
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	26,202	33,583
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 135,457	$ 79,479