CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 433.6	$ 425.5	$ 619.0
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation and amortization	355.0	321.6	283.5
Deferred income taxes and investment tax credits, net	27.6	78.5	(50.0)
Equity in earnings of unconsolidated affiliates	(113.9)	(152.8)	(131.2)
Distributions from unconsolidated affiliates	125.5	141.2	131.2
Allowance for equity funds used during construction	(4.5)	(23.8)	(39.7)
Stock-based compensation expense	13.9	13.4	9.1
Regulatory assets	47.1	10.8	(3.7)
Regulatory liabilities	(45.6)	(16.5)	(3.7)
Other assets	(3.8)	6.2	(0.7)
Other liabilities	19.2	1.0	(65.5)
Change in certain current assets and liabilities:
Accounts receivable and accrued unbilled revenues, net	18.8	19.8	(21.8)
Income taxes receivable	(1.0)	(4.1)	13.6
Fuel, materials and supplies inventories	4.2	27.3	(3.6)
Fuel recoveries	(33.0)	(3.4)	53.0
Other current assets	5.1	25.1	27.2
Accounts payable	(34.5)	29.7	27.1
Other current liabilities	(38.0)	73.2	(66.7)
Net cash provided from operating activities	681.5	951.1	784.5
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures (less allowance for equity funds used during construction)	(635.5)	(573.6)	(824.1)
Investment in unconsolidated affiliates	(7.7)	(2.5)	(8.5)
Return of capital - unconsolidated affiliates	18.5	0.0	10.0
Proceeds from sale of assets	0.0	0.1	0.7
Net cash used in investing activities	(624.7)	(576.0)	(821.9)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (decrease) in short-term debt	112.0	(168.4)	(67.8)
Proceeds from long-term debt	296.5	396.0	592.1
Payment of long-term debt	(250.1)	(250.1)	(225.1)
Dividends paid on common stock	(299.2)	(272.2)	(247.6)
Cash paid for employee equity-based compensation and expense of common stock	(10.3)	(0.5)	(0.1)
Net cash provided from (used in) financing activities	(151.1)	(295.2)	51.5
NET CHANGE IN CASH AND CASH EQUIVALENTS	(94.3)	79.9	14.1
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	94.3	14.4	0.3
CASH AND CASH EQUIVALENTS AT END OF YEAR	$ 0.0	$ 94.3	$ 14.4