CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 324.2	$ 280.3
Adjustments to reconcile net income to net cash provided from operating activities
Depreciation and amortization	207.2	240.8
Deferred income taxes and investment tax credits, net	152.1	134.2
Equity in earnings of unconsolidated affiliates	(98.6)	(79.5)
Distributions from unconsolidated affiliates	98.6	79.9
Allowance for equity funds used during construction	(27.2)	(9.2)
Stock-based compensation	4.7	3.2
Regulatory assets	10.9	(10.5)
Regulatory liabilities	(0.6)	(9.8)
Other assets	(2.0)	18.0
Other liabilities	(70.8)	(19.8)
Change in certain current assets and liabilities
Accounts receivable, net	(87.2)	(51.9)
Accrued unbilled revenues	(10.1)	(17.5)
Fuel, materials and supplies inventories	4.1	30.9
Fuel clause under recoveries	15.8	(0.5)
Other current assets	26.8	(13.1)
Accounts payable	(29.1)	(90.6)
Fuel clause over recoveries	0.0	(59.9)
Other current liabilities	(55.1)	1.9
Net cash provided from operating activities	463.7	426.9
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)	(662.8)	(466.7)
Investments in and Advances to Affiliates, at Fair Value, Period Increase (Decrease)	(5.2)	0.0
Return of capital - equity method investments	7.3	25.9
Proceeds from sale of assets	0.4	0.3
Net cash used in investing activities	(660.3)	(440.5)
CASH FLOWS FROM FINANCING ACTIVITIES
Dividends paid on common stock	(181.2)	(164.7)
Proceeds from long-term debt	592.3	0.0
Payment of long-term debt	(125.1)	(110.1)
Increase (decrease) in short-term debt	(89.7)	213.2
Net cash provided from (used in) financing activities	196.3	(61.6)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(0.3)	(75.2)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	0.3	75.2
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 0.0	$ 0.0