CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 320.4	$ 266.6
Adjustments to reconcile net income to net cash provided from operating activities
Depreciation and amortization	225.8	215.2
Impairment of assets	5.0	0
Deferred income taxes and investment tax credits, net	146.1	146.8
Allowance for equity funds used during construction	(16.1)	(7.2)
(Gain) loss on disposition and abandonment of assets	(2.8)	0.9
Stock-based compensation expense	3.4	4.9
Excess tax benefit on stock-based compensation	0	(0.7)
Price risk management assets	0.1	2.3
Price risk management liabilities	12.0	6.2
Regulatory assets	9.6	15.4
Regulatory liabilities	0.6	(10.3)
Other assets	(5.4)	5.4
Other liabilities	(41.3)	(10.9)
Change in certain current assets and liabilities
Accounts receivable, net	(118.5)	(48.0)
Accrued unbilled revenues	(9.8)	(11.2)
Income taxes receivable	(3.6)	141.2
Fuel, materials and supplies inventories	61.5	(12.3)
Gas imbalance assets	(0.1)	0
Fuel clause under recoveries	(32.2)	(0.6)
Other current assets	7.1	7.8
Accounts payable	(40.9)	(13.7)
Gas imbalance liabilities	(1.1)	(1.0)
Fuel clause over recoveries	(21.4)	(119.5)
Other current liabilities	30.3	9.6
Net Cash Provided from Operating Activities	528.7	586.9
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)	(907.3)	(612.5)
Reimbursement of capital expenditures	37.2	24.5
Proceeds from sale of assets	17.8	1.9
Other investing activities	0	0.1
Net Cash Used in Investing Activities	(852.3)	(586.0)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from long-term debt	246.3	246.2
Increase in short-term debt	144.0	49.0
Contributions from noncontrolling interest partners	73.5	0
Issuance of common stock	11.0	13.5
Proceeds from line of credit	0	115.0
Excess tax benefit on stock-based compensation	0	0.7
Retirement of long-term debt	0	(289.2)
Distributions to noncontrolling interest partners	(12.8)	0
Repayment of line of credit	(25.0)	(80.0)
Dividends paid on common stock	(110.1)	(105.7)
Net Cash Provided from (Used in) Financing Activities	326.9	(50.5)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	3.3	(49.6)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	2.3	58.1
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 5.6	$ 8.5