CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities
Net income	$ 356.9	$ 346.5
Reconciliation to cash provided by operating activities
Depreciation and amortization	194.6	191.9
Deferred income taxes and investment tax credits, net	150.2	214.6
Contributions and payments related to pension and OPEB plans	(106.0)	(15.1)
Equity income in transmission affiliate, net of distributions	(6.7)	(23.4)
Change in -
Accounts receivable and unbilled revenues	55.0	(48.6)
Materials, supplies, and inventories	170.5	217.2
Other current assets	41.2	(63.7)
Accounts payable	(212.7)	(123.7)
Other current liabilities	90.8	56.7
Other, net	(19.2)	(56.5)
Net cash provided by operating activities	714.6	695.9
Investing Activities
Capital expenditures	(329.7)	(312.0)
Capital contributions to transmission affiliate	(27.6)	(9.0)
Proceeds from the sale of assets and businesses	13.1	106.5
Withdrawal of restricted cash from Rabbi trust for qualifying payments	16.1	21.0
Other, net	2.5	5.1
Net cash used in investing activities	(325.6)	(188.4)
Financing Activities
Exercise of stock options	5.9	21.4
Purchase of common stock	(20.2)	(59.6)
Dividends paid on common stock	(164.1)	(156.2)
Retirement of long-term debt	(12.0)	(139.4)
Change in short-term debt	(189.8)	(198.6)
Other, net	(0.6)	9.8
Net cash used in financing activities	(380.8)	(522.6)
Net change in cash and cash equivalents	8.2	(15.1)
Cash and cash equivalents at beginning of period	37.5	49.8
Cash and cash equivalents at end of period	$ 45.7	$ 34.7