CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	$ 366,940	$ 370,209	$ 72,764
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of energy-related products and services business	(10,404)
Gain on sale of district cooling business		(41,973)
Depreciation and amortization including nuclear fuel	493,784	472,807	450,864
Deferred fuel and purchased power	69,166	93,631	(51,742)
Deferred fuel and purchased power amortization	(155,157)	(122,481)	147,018
Allowance for equity funds used during construction	(23,707)	(22,066)	(14,999)
Real estate impairment charges		16,731	280,188
Gain on real estate debt restructuring		(16,755)
Deferred income taxes	176,192	260,411	105,492
Change in mark-to-market valuations	4,064	2,688	(6,939)
Changes in current assets and liabilities:
Customer and other receivables	40,626	(67,943)	12,292
Accrued unbilled revenues	(21,947)	7,679	(10,882)
Materials, supplies and fossil fuel	(23,398)	12,276	(12,261)
Other current assets	(3,079)	9,375	38,406
Accounts payable	58,346	9,125	(27,328)
Accrued taxes and income tax receivable - net	12,068	24,222	(31,792)
Other current liabilities	20,358	2,921	57,280
Change in margin and collateral accounts - assets	33,349	(9,937)	(12,806)
Change in margin and collateral accounts - liabilities	29,731	(88,315)	35,654
Change in long term income tax receivable	(3,530)		(131,984)
Change in unrecognized tax benefits	8,410	(73,621)	137,898
Change in other regulatory liabilities	37,009	56,801	82,650
Change in other long-term assets	(41,722)	(47,940)	(64,629)
Change in other long-term liabilities	58,484	(97,388)	12,161
Net cash flow provided by operating activities	1,125,583	750,457	1,067,305
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(884,350)	(748,374)	(764,609)
Contributions in aid of construction	38,096	32,754	53,525
Allowance for borrowed funds used during construction	(18,358)	(16,778)	(10,745)
Proceeds from sale of district cooling business		100,300
Proceeds from sale of energy-related products and services business	45,111
Proceeds from nuclear decommissioning trust sales	497,780	560,469	441,242
Investment in nuclear decommissioning trust	(513,799)	(584,885)	(463,033)
Proceeds from sale of commercial real estate investments	1,375	72,038	43,370
Proceeds from sale of life insurance policies	55,444
Other	(3,306)	8,576	(4,667)
Net cash flow used for investing activities	(782,007)	(575,900)	(704,917)
CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of long-term debt	470,353		867,469
Repayment of long-term debt	(655,169)	(106,572)	(456,882)
Short-term borrowings and payments - net	(16,600)	(137,115)	(516,754)
Dividends paid on common stock	(221,728)	(216,979)	(205,076)
Common stock equity issuance	15,841	255,971	3,302
Distributions to noncontrolling interests	(10,210)	(11,403)	(14,485)
Other	(2,668)	6,351	171
Net cash flow used for financing activities	(420,181)	(209,747)	(322,255)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(76,605)	(35,190)	40,133
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	110,188	145,378	105,245
CASH AND CASH EQUIVALENTS AT END OF YEAR	33,583	110,188	145,378
Cash paid during the period for:
Income taxes, net of (refunds)	10,324	(23,447)	(52,776)
Interest, net of amounts capitalized	$ 217,789	$ 221,728	$ 216,608