CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 28.0	$ 47.5
Adjustments to reconcile net income to net cash provided from operating activities
Depreciation and amortization	92.9	87.6
Impairment of assets	0	0.2
Deferred income taxes and investment tax credits, net	15.4	18.4
Allowance for equity funds used during construction	(1.2)	(1.9)
(Gain) loss on disposition and abandonment of assets	(8.7)	0.5
Gain on insurance proceeds	0	(7.5)
Stock-based compensation	(8.3)	(11.8)
Price risk management assets	0.1	(0.5)
Price risk management liabilities	0.1	(4.9)
Regulatory assets	5.5	5.6
Regulatory liabilities	(4.1)	(3.4)
Other assets	(0.1)	1.4
Other liabilities	6.3	5.2
Change in certain current assets and liabilities
Accounts receivable, net	8.4	54.8
Accrued unbilled revenues	7.8	6.0
Fuel, materials and supplies inventories	(7.7)	3.3
Gas imbalance assets	(3.7)	(4.0)
Fuel clause under recoveries	(0.4)	1.8
Other current assets	(4.1)	(6.3)
Accounts payable	16.5	(59.2)
Gas imbalance liabilities	0.7	(1.5)
Fuel clause over recoveries	(27.6)	31.5
Other current liabilities	(56.6)	(42.5)
Net Cash Provided from Operating Activities	59.2	120.3
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)	(325.1)	(311.1)
Proceeds from insurance	0	6.1
Reimbursement of capital expenditures	0	9.7
Proceeds from sale of assets	35.6	0.2
Net Cash Used in Investing Activities	(289.5)	(295.1)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase in short-term debt	276.1	212.2
Issuance of common stock	3.2	3.7
Distributions to noncontrolling interest partners	(2.5)	(5.6)
Dividends paid on common stock	(41.2)	(38.5)
Net Cash Provided from Financing Activities	235.6	171.8
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	5.3	(3.0)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	1.8	4.6
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 7.1	$ 1.6