CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Operating activities
Net income	$ 366,953	$ 362,331
Remove income from discontinued operations	(109)	(193)
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	464,117	463,013
Conservation and demand side management program amortization	3,765	6,078
Nuclear fuel amortization	49,765	43,732
Deferred income taxes	278,358	197,637
Amortization of investment tax credits	(3,104)	(3,160)
Allowance for equity funds used during construction	(28,644)	(26,850)
Equity earnings of unconsolidated subsidiaries	(14,660)	(15,390)
Dividends from unconsolidated subsidiaries	8,028	16,931
Share-based compensation expense	17,249	20,299
Net derivative losses	7,325	16,802
Changes in operating assets and liabilities:
Accounts receivable	(928)	38,914
Accrued unbilled revenues	139,012	117,836
Inventories	145,095	76,028
Other current assets	(61,291)	52,397
Accounts payable	(177,076)	32,116
Net regulatory assets and liabilities	12,912	(41,888)
Other current liabilities	(117,653)	(78,110)
Pension and other employee benefit obligations	(168,898)	(131,892)
Change in other noncurrent assets	(40,893)	13,119
Change in other noncurrent liabilities	(14,027)	(36,634)
Net cash provided by operating activities	865,296	1,123,116
Investing activities
Utility capital/construction expenditures	(1,103,562)	(1,122,269)
Proceeds from insurance recoveries	24,000	0
Merricourt refund	0	101,261
Merricourt deposit	0	(90,833)
Allowance for equity funds used during construction	28,644	26,850
Purchases of investments in external decommissioning fund	(371,361)	(1,226,504)
Proceeds from the sale of investments in external decommissioning fund	371,361	1,226,491
Investment in WYCO Development LLC	(379)	(961)
Change in restricted cash	94,959	46
Other, net	(24)	(3,964)
Net cash used in investing activities	(956,362)	(1,089,883)
Financing activities
Proceeds from short-term borrowings, net	262,000	189,600
Proceeds from issuance of long-term debt	111,015	0
Repayments of long-term debt, including reacquisition premiums	(2,455)	(1,741)
Proceeds from issuance of common stock	3,698	3,789
Repurchase of common stock	(18,529)	0
Purchase of common stock for settlement of equity awards	(23,307)	0
Dividends paid	(238,510)	(231,715)
Net cash provided by (used in) financing activities	93,912	(40,067)
Net change in cash and cash equivalents	2,846	(6,834)
Cash and cash equivalents at beginning of period	60,684	108,437
Cash and cash equivalents at end of period	63,530	101,603
Supplemental disclosure of cash flow information:
Cash paid for interest (net of amounts capitalized)	(281,266)	(266,559)
Cash (paid) received for income taxes, net	(5,875)	54,993
Supplemental disclosure of non-cash investing and financing transactions:
Property, plant and equipment additions in accounts payable	274,350	120,558
Issuance of common stock for reinvested dividends and 401(k) plans	$ 35,543	$ 37,680