Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Cash Flows [Abstract]
Net income	$ 365.5	$ 376.9	$ 377.9
Reconciliation to cash provided by operating activities
Depreciation and amortization	325.4	323.7	302.6
Deferred income taxes and investment tax credits, net	206.2	178.9	191.4
Contributions and payments related to pension and OPEB plans	(8.0)	(107.6)	(10.4)
Equity income in transmission affiliate, net of distributions	(17.2)	(4.9)	(7.4)
Payments for liabilities transferred to WBS	(116.0)	0.0	0.0
Change In
Accounts receivable and unbilled revenues	(59.0)	(2.9)	91.0
Material, supplies, and inventories	30.6	18.8	(39.5)
Prepaid taxes	39.4	(2.8)	(2.5)
Other current assets	9.3	0.3	(6.2)
Accounts payable	31.3	(5.9)	18.2
Accrued taxes	30.4	(42.1)	(7.5)
Other current liabilities	10.7	(1.2)	(36.8)
Other, net	(0.2)	(56.8)	(8.0)
Net cash provided by operating activities	848.4	674.4	862.8
Investing Activities
Capital expenditures	(469.5)	(519.2)	(561.8)
Capital contributions to transmission affiliate	(16.1)	(4.6)	(11.5)
Proceeds from the sale of assets	31.7	0.2	6.0
Proceeds from assets transferred to WBS	13.1	0.0	0.0
Other, net	4.0	3.4	(0.2)
Net cash used in investing activities	(436.8)	(520.2)	(567.5)
Financing Activities
Dividends paid on common stock	(455.0)	(240.0)	(390.0)
Dividends paid on preferred stock	(1.2)	(1.2)	(1.2)
Issuance of long-term debt	0.0	500.0	250.0
Retirement of long-term debt	0.0	(250.0)	(300.0)
Change in short-term debt	15.0	(162.8)	131.9
Repayment of subsidiary note WEC Energy Group	(1.1)	(2.9)	0.0
Other, net	19.0	5.8	12.9
Net cash used in financing activities	(423.3)	(151.1)	(296.4)
Net change in cash and cash equivalents	(11.7)	3.1	(1.1)
Cash and cash equivalents at beginning of year	27.1	24.0	25.1
Cash and cash equivalents at end of year	$ 15.4	$ 27.1	$ 24.0