CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 172,434	$ 129,630
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization including nuclear fuel	249,482	239,743
Deferred fuel and purchased power	36,183	82,261
Deferred fuel and purchased power amortization	10,921	(54,388)
Allowance for equity funds used during construction	(13,129)	(9,931)
Deferred income taxes	68,526	61,109
Deferred investment tax credit	20,159	5,033
Change in derivative instruments fair value	349	(2,618)
Changes in current assets and liabilities:
Customer and other receivables	(79,408)	(21,424)
Accrued unbilled revenues	(68,763)	(43,211)
Materials, supplies and fossil fuel	(4,002)	(21,012)
Other current assets	(14,439)	(9,407)
Accounts payable	85,563	9,199
Accrued taxes and income tax receivable - net	5,032	19,775
Other current liabilities	(26,098)	807
Change in margin and collateral accounts - assets	(1,111)	124
Change in margin and collateral accounts - liabilities	14,600	69,602
Change in other long-term assets	(23,796)	(1,692)
Change in other long-term liabilities	21,753	5,035
Net cash flow provided by operating activities	454,256	458,635
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(376,601)	(424,775)
Contributions in aid of construction	21,236	25,800
Allowance for borrowed funds used during construction	(7,626)	(6,598)
Proceeds from nuclear decommissioning trust sales	253,996	211,138
Investment in nuclear decommissioning trust	(262,621)	(219,762)
Other	(262)	(525)
Net cash flow used for investing activities	(371,878)	(414,722)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	136,307	351,081
Repayment of long-term debt	(40,127)	(421,451)
Short-term borrowings and payments - net	(62,075)	109,000
Dividends paid on common stock	(116,231)	(111,297)
Common stock equity issuance	9,751	8,869
Distributions to noncontrolling interests	(9,197)	(2,630)
Other	795	160
Net cash flow used for financing activities	(80,777)	(66,268)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	1,601	(22,355)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	26,202	33,583
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 27,803	$ 11,228