CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities
Net income	$ 236,570	$ 183,893
Remove loss (income) from discontinued operations	18	(124)
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	253,004	233,097
Conservation and demand side management program amortization	1,712	1,882
Nuclear fuel amortization	27,522	26,000
Deferred income taxes	130,662	167,426
Amortization of investment tax credits	(1,657)	(1,552)
Allowance for equity funds used during construction	(19,754)	(13,450)
Equity earnings of unconsolidated subsidiaries	(7,577)	(7,158)
Dividends from unconsolidated subsidiaries	9,539	8,028
Share-based compensation expense	8,167	3,883
Net realized and unrealized hedging and derivative transactions	217	7,133
Changes in operating assets and liabilities:
Accounts receivable	(72,205)	(52,643)
Accrued unbilled revenues	76,602	197,330
Inventories	87,865	143,873
Other current assets	(51,203)	(71,547)
Accounts payable	5,311	(202,649)
Net regulatory assets and liabilities	88,572	61,872
Other current liabilities	20,318	17,711
Pension and other employee benefit obligations	(181,091)	(180,030)
Change in other noncurrent assets	24,576	(38,806)
Change in other noncurrent liabilities	5,160	(6,686)
Net cash provided by operating activities	642,328	477,483
Investing activities
Utility capital/construction expenditures	(752,251)	(497,218)
Proceeds from insurance recoveries	23,500	0
Allowance for equity funds used during construction	19,754	13,450
Purchases of investments in external decommissioning fund	(586,239)	(213,618)
Proceeds from the sale of investments in external decommissioning fund	584,948	213,618
Investment in WYCO Development LLC	(231)	(172)
Change in restricted cash	0	86,232
Other, net	(2,745)	(1,304)
Net cash used in investing activities	(713,264)	(399,012)
Financing activities
(Repayments of) proceeds from short-term borrowings, net	(177,000)	120,000
Proceeds from issuance of long-term debt	494,282	745
Repayments of long-term debt, including reacquisition premiums	(251,367)	(758)
Proceeds from issuance of common stock	160,084	1,598
Repurchase of common stock	0	(18,529)
Purchase of common stock for settlement of equity awards	0	(23,307)
Dividends paid	(124,426)	(119,162)
Net cash provided by (used in) financing activities	101,573	(39,413)
Net change in cash and cash equivalents	30,637	39,058
Cash and cash equivalents at beginning of period	82,323	60,684
Cash and cash equivalents at end of period	112,960	99,742
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(153,498)	(156,275)
Cash received (paid) for income taxes, net	17,939	(1,173)
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	256,530	224,316
Issuance of common stock for reinvested dividends and 401(k) plans	$ 18,791	$ 18,815