Condensed Parent Company Financial Statements (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities
Net income	$ 577.4	$ 546.3	$ 526.2
Reconciliation to cash
Deferred income taxes, net	313.8	294.4	434.8
Accrued income taxes, net	36.6	116.9	(87.4)
Other current assets	2.8	12.1	(20.5)
Other current liabilities	7.2	(14.9)	44.1
Accounts receivable and accrued revenues	(162.9)	38.3	30.1
Other, net	49.2	(164.0)	(23.5)
Cash Provided by Operating Activities	1,231.0	1,173.9	993.4
Investing Activities
Proceeds from asset sales	2.5	8.7	41.5
Capital contributions to associated companies	(10.5)	(15.7)	(6.6)
Cash Used in Investing Activities	(745.8)	(729.6)	(892.5)
Financing Activities
Exercise of stock options	48.5	49.8	54.4
Purchase of common stock	(223.4)	(153.2)	(193.9)
Dividends paid on common stock	(328.9)	(276.3)	(242.0)
Issuance of long-term debt	251.0	251.8	720.0
Retirement and repurchase of long-term debt	(397.2)	(20.3)	(466.6)
Change in short-term debt	142.8	(275.3)	12.0
Other, net	12.4	0.7	4.8
Cash Used in Financing Activities	(494.8)	(422.8)	(111.3)
Change in Cash and Cash Equivalents	(9.6)	21.5	(10.4)
Cash and Cash Equivalents at Beginning of Year	35.6	14.1	24.5
Cash and Cash Equivalents at End of Year	26.0	35.6	14.1
Wisconsin Energy Corporation [Member]
Operating Activities
Net income	577.4	546.3	526.2
Reconciliation to cash
Equity in susidiaries' earnings	(607.8)	(577.6)	(545.9)
Dividends and distributions from subsidiaries	720.4	842.3	995.5
Deferred income taxes, net	(7.8)	104.4	(350.9)
Accrued income taxes, net	66.8	(457.9)	363.4
Other current assets	(0.1)	0.2	(0.1)
Other current liabilities	(22.9)	(6.7)	8.9
Accounts receivable and accrued revenues	(2.7)	22.5	(18.7)
Other, net	(21.6)	(8.1)	(10.2)
Cash Provided by Operating Activities	701.7	465.4	968.2
Investing Activities
Capital contributions to associated companies	(195.3)	(21.5)	(36.5)
Capitalized interest and other	4.0	12.6	2.4
Cash Used in Investing Activities	(191.3)	(8.9)	(34.1)
Financing Activities
Exercise of stock options	48.5	49.8	54.4
Purchase of common stock	(223.4)	(153.9)	(193.9)
Dividends paid on common stock	(328.9)	(276.3)	(242.0)
Retirement and repurchase of long-term debt	0	0	(450.0)
Change in short-term debt	5.0	(79.5)	(116.5)
Change in notes payable due associated companies	(26.8)	3.8	3.9
Other, net	14.6	0	9.9
Cash Used in Financing Activities	(511.0)	(456.1)	(934.2)
Change in Cash and Cash Equivalents	(0.6)	0.4	(0.1)
Cash and Cash Equivalents at Beginning of Year	0.9	0.5	0.6
Cash and Cash Equivalents at End of Year	$ 0.3	$ 0.9	$ 0.5