CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 149.1	$ 139.0
Adjustments to reconcile net income to net cash provided from operating activities
Depreciation and amortization	177.1	148.7
Impairment of assets	0.3	0
Deferred income taxes and investment tax credits, net	63.1	60.3
Allowance for equity funds used during construction	(3.6)	(10.2)
(Gain) loss on disposition and abandonment of assets	0.7	(3.3)
Gain on insurance proceeds	(7.5)	0
Stock-based compensation	(9.4)	0.4
Price risk management assets	2.8	1.1
Price risk management liabilities	(5.4)	6.8
Regulatory assets	10.3	6.8
Regulatory liabilities	(7.6)	3.3
Other assets	4.8	5.4
Other liabilities	(26.6)	(38.3)
Change in certain current assets and liabilities
Accounts receivable, net	19.9	(47.0)
Accrued unbilled revenues	(25.3)	(39.8)
Income taxes receivable	(8.8)	0
Fuel, materials and supplies inventories	(3.6)	33.9
Gas imbalance assets	(8.3)	(3.6)
Fuel clause under recoveries	1.1	(21.4)
Other current assets	(13.0)	3.5
Accounts payable	(92.6)	(6.1)
Gas imbalance liabilities	(8.3)	1.0
Fuel clause over recoveries	57.7	(20.6)
Other current liabilities	14.6	26.6
Net Cash Provided from Operating Activities	281.5	246.5
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)	(558.5)	(571.8)
Reimbursement of capital expenditures	23.4	21.6
Proceeds from insurance	7.6	0
Proceeds from sale of assets	0.6	17.5
Net Cash Used in Investing Activities	(526.9)	(532.7)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase in short-term debt	319.6	66.1
Issuance of common stock	7.0	7.5
Contributions from noncontrolling interest partners	1.0	73.5
Proceeds from long-term debt	0	246.3
Repayment of line of credit	0	(25.0)
Distributions to noncontrolling interest partners	(8.0)	(6.1)
Dividends paid on common stock	(77.1)	(73.3)
Net Cash Provided from Financing Activities	242.5	289.0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(2.9)	2.8
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	4.6	2.3
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 1.7	$ 5.1