Wisconsin Electric Power Company PFD 3.60% (WELPP) 10-K 27 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Jan. 31, 2015	Jun. 30, 2014
Entity Information [Line Items]
Entity Registrant Name	WISCONSIN ELECTRIC POWER CO
Entity Central Index Key	107815
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		33,289,327
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$25.80

Consolidated_Income_Statements

Consolidated Income Statements (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Operating Revenues	$4,059.40		$3,800.20		$3,613.30
Operating Expenses
Fuel and purchased power	1,228.10		1,158.10		1,103.80
Cost of gas sold	432.6		278.3		227.7
Other operation and maintenance	1,356.40		1,417.30		1,327.80
Depreciation and amortization	295.7		278.6		257.6
Property and revenue taxes	113.6		110		113.1
Total Operating Expenses	3,426.40		3,242.30		3,030
Treasury Grant	17.4		48		0
Operating Income	650.4	[1]	605.9	[1]	583.3	[1]
Equity in Earnings of Transmission Affiliate	57.9		60.2		57.6
Other Income and Deductions, net	8.7		17.4		32.3
Interest Expense, net	116.5		121.4		113.2
Income Before Income Taxes	600.5		562.1		560
Total Income Tax Expense, Amount	222.6		200.9		192.7
Net Income	377.9		361.2		367.3
Preferred Stock Dividend Requirement	1.2		1.2		1.2
Earnings Available for Common Stockholder	$376.70		$360		$366.10
[1]	We evaluate operating income to manage our utility business. Equity in Earnings of Transmission Affiliate, Interest Expense and Income Taxes are not included in segment operating income.

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Property, Plant and Equipment
Electric	$9,024.80	$8,717
Gas	1,025.40	977.4
Steam	101.5	102
Common	339.6	307.4
Other	53.1	56.8
Property, Plant and Equipment in Service, Gross	10,544.40	10,160.60
Accumulated depreciation	-3,406.10	-3,258.80
Property, Plant and Equipment in Service, Net	7,138.30	6,901.80
Construction work in progress	140.9	101.9
Leased facilities, net	2,215	2,279
Net Property, Plant and Equipment	9,494.20	9,282.70
Investments
Equity investment in transmission affiliate	372.9	354.1
Other	0.2	0.2
Total Investments	373.1	354.3
Current Assets
Cash and cash equivalents	24	25.1
Accounts receivable, net of allowance for doubtful accounts of $46.8 and $39.7	265.3	335.7
Accounts receivable from related parties	8.1	9.1
Accrued revenues	223.1	240.7
Materials, supplies and inventories	320.5	281
Deferred Tax Assets, Net, Current	46.7	75.8
Prepayments	139.5	137.7
Other	19	8.7
Total Current Assets	1,046.20	1,113.80
Deferred Charges and Other Assets
Regulatory assets	1,626.90	1,370.30
Other	106.3	164.5
Total Deferred Charges and Other Assets	1,733.20	1,534.80
Total Assets	12,646.70	12,285.60
Capitalization
Common equity	3,412.80	3,406.80
Preferred stock	30.4	30.4
Long-term debt	2,165.50	2,167.30
Capital lease obligations	2,712.50	2,712
Total Capitalization	8,321.20	8,316.50
Current Liabilities
Long-term debt and capital lease obligations due currently	355.6	379.5
Short-term debt	306.8	174.5
Subsidiary note payable to Wisconsin Energy	22.4	22.8
Accounts payable	287.2	273.8
Accounts payable to related parties	87.8	85.9
Accrued payroll and benefits	87.1	89.3
Other	113.7	132.3
Total Current Liabilities	1,260.60	1,158.10
Deferred Credits and Other Liabilities
Regulatory liabilities	615.9	634.2
Deferred income taxes - long term	1,963.90	1,794.50
Pension and other benefit obligations	254.5	160.1
Other	230.6	222.2
Total Deferred Credits and Other Liabilities	3,064.90	2,811
Commitments and Contingencies (Note Q)
Total Capitalization and Liabilities	$12,646.70	$12,285.60

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets Parenthetical (Parentheticals) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Allowance for doubtful accounts receivable	$46.80	$39.70

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities
Net Income	$377.90	$361.20	$367.30
Reconciliation to cash
Depreciation and amortization	303.4	288.3	263.6
Deferred income taxes and investment tax credits, net	191.4	193.6	194.1
Contributions to qualified benefit plans	0	0	-92.9
Change In
Accounts receivable and accrued revenues	91	-137	64.3
Inventories	-39.5	31.2	7
Other current assets	-8.7	0.7	6.9
Accounts payable	18.2	-29.4	41.4
Accrued income taxes, net	-7.5	23.6	89.4
Deferred costs, net	-15.1	-8.7	9.2
Other current liabilities	-21.7	21.8	-2.4
Other, net	-26.6	117.3	-140.9
Cash Provided by Operating Activities	862.8	862.6	807
Investing Activities
Capital expenditures	-540.9	-506.9	-575.8
Investment in transmission affiliate	-11.5	-9.2	-13.8
Change in restricted cash	0	2.7	42.8
(Payments) for Proceeds from Removal Costs	-20.9	-32	-32.9
Other, net	5.8	-14.7	-25.9
Cash Used in Investing Activities	-567.5	-560.1	-605.6
Financing Activities
Dividends paid on common stock	-390	-340	-179.6
Dividends paid on preferred stock	-1.2	-1.2	-1.2
Issuance of long-term debt	250	250	250
Retirement of long-term debt	-300	-300	0
Change in total short-term debt	131.9	68.4	-249.9
Other, net	12.9	11.3	0.7
Cash (Used in) Provided by Financing Activities	-296.4	-311.5	-180
Change in Cash and Cash Equivalents	-1.1	-9	21.4
Cash and Cash Equivalents at Beginning of Year	25.1	34.1	12.7
Cash and Cash Equivalents at End of Year	$24	$25.10	$34.10

Consolidated_Statements_of_Cap

Consolidated Statements of Capitalization (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Common stock - $10 par value; authorized 65,000,000 shares; outstanding - 33,289,327 shares	$3,412.80	$3,406.80
Other paid in capital	984.4	965.1
Retained earnings	2,095.50	2,108.80
Total Common Equity	3,412.80	3,406.80
Preferred stock	30.4	30.4
Long-term Debt, unsecured	147
Unamortized discount, net	21.5	19.7
Long-term Debt due currently	-250	-300
Total long-term debt	2,165.50	2,167.30
Obligations under capital leases	2,712.50	2,712
Total Capitalization	8,321.20	8,316.50
Debentures (unsecured), 6.00% due 2014 [Member]
Long-term Debt, unsecured	0	300
Debentures (unsecured), 6.25% due 2015 [Member]
Long-term Debt, unsecured	250	250
Debentures (unsecured), 1.70% due 2018 [Member]
Long-term Debt, unsecured	250	250
Debentures (unsecured), 4.25% due 2019 [Member]
Long-term Debt, unsecured	250	250
Debentures (unsecured) 2.95% due 2021 [Member]
Long-term Debt, unsecured	300	300
Debentures (unsecured), 6-1/2% due 2028 [Member]
Long-term Debt, unsecured	150	150
Debentures (unsecured), 5.625% due 2033 [Member]
Long-term Debt, unsecured	335	335
Debentures (unsecured), 5.70% due 2036 [Member]
Long-term Debt, unsecured	300	300
Debentures (unsecured), 3.65% due 2042 [Member]
Long-term Debt, unsecured	250	250
Debentures (unsecured), 4.25% due 2044 [Member]
Long-term Debt, unsecured	250	0
Debentures (unsecured), 6-7/8% due 2095 [Member]
Long-term Debt, unsecured	100	100
Notes (secured, nonrecourse), 4.81% effective rate due 2030 [Member]
Long-term Debt, secured	2	2
Common Stock [Member]
Common stock - $10 par value; authorized 65,000,000 shares; outstanding - 33,289,327 shares	332.9	332.9
Six Per Cent. Preferred Stock [Member]
Preferred stock	4.4	4.4
Serial preferred stock, 3.60% Series Redeemable [Member]
Preferred stock	26	26
Serial preferred stock, $25 par value; authorized 5,000,000 shares; none outstanding [Member]
Preferred stock	$0	$0

Consolidated_Statements_of_Cap1

Consolidated Statements of Capitalization (Parenthetical) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Long-term Debt, unsecured	$147
Common Stock, par value	$10	$10
Common Stock, shares authorized	65,000,000	65,000,000
Common Stock, shares, outstanding	33,289,327	33,289,327
Debentures (unsecured), 6.00% due 2014 [Member]
Long-term Debt, unsecured	0	300
Long term debt, interest rate stated percentage	6.00%	6.00%
Debentures (unsecured), 6.25% due 2015 [Member]
Long-term Debt, unsecured	250	250
Long term debt, interest rate stated percentage	6.25%	6.25%
Debentures (unsecured), 1.70% due 2018 [Member]
Long-term Debt, unsecured	250	250
Long term debt, interest rate stated percentage	1.70%	1.70%
Debentures (unsecured), 4.25% due 2019 [Member]
Long-term Debt, unsecured	250	250
Long term debt, interest rate stated percentage	4.25%	4.25%
Debentures (unsecured) 2.95% due 2021 [Member]
Long-term Debt, unsecured	300	300
Long term debt, interest rate stated percentage	2.95%	2.95%
Debentures (unsecured), 6-1/2% due 2028 [Member]
Long-term Debt, unsecured	150	150
Long term debt, interest rate stated percentage	6.50%	6.50%
Debentures (unsecured), 5.625% due 2033 [Member]
Long-term Debt, unsecured	335	335
Long term debt, interest rate stated percentage	5.63%	5.63%
Debentures (unsecured), 5.70% due 2036 [Member]
Long-term Debt, unsecured	300	300
Long term debt, interest rate stated percentage	5.70%	5.70%
Debentures (unsecured), 3.65% due 2042 [Member]
Long-term Debt, unsecured	250	250
Long term debt, interest rate stated percentage	3.65%	3.65%
Debentures (unsecured), 4.25% due 2044 [Member]
Long-term Debt, unsecured	250	0
Long term debt, interest rate stated percentage	4.25%	4.25%
Debentures (unsecured), 6-7/8% due 2095 [Member]
Long-term Debt, unsecured	$100	$100
Long term debt, interest rate stated percentage	6.88%	6.88%
Notes (secured, nonrecourse), 4.81% effective rate due 2030 [Member]
Long term debt, interest rate stated percentage	4.81%	4.81%
Six Per Cent. Preferred Stock [Member]
Preferred stock, par value	$100	$100
Preferred stock, shares authorized	45,000	45,000
Preferred stock, shares outstanding	44,498	44,498
Preferred stock dividend rate, percentage	6.00%	6.00%
Serial preferred stock, 3.60% Series Redeemable [Member]
Preferred stock, par value	$100	$100
Preferred stock, shares outstanding	260,000	260,000
Preferred stock dividend rate, percentage	3.60%	3.60%

Consolidated_Statements_of_Com

Consolidated Statements of Common Equity (USD $)	Total	Common Stock [Member]	Other Additional Capital [Member]	Retained Earnings [Member]
In Millions, unless otherwise specified
Beginning - Balance at Dec. 31, 2011	$3,177.10	$332.90	$941.90	$1,902.30
Net income	367.3			367.3
Cash dividends
Common stock	-179.6			-179.6
Preferred stock	-1.2			-1.2
Stock-based compensation	2.8		2.8
Tax benefit of exercised stock options allocated from Parent	0		0
Ending - Balance at Dec. 31, 2012	3,366.40	332.9	944.7	2,088.80
Net income	361.2			361.2
Cash dividends
Common stock	-340			-340
Preferred stock	-1.2			-1.2
Stock-based compensation	3.7		3.7
Tax benefit of exercised stock options allocated from Parent	16.7		16.7
Ending - Balance at Dec. 31, 2013	3,406.80	332.9	965.1	2,108.80
Net income	377.9			377.9
Cash dividends
Common stock	-390			-390
Preferred stock	-1.2			-1.2
Stock-based compensation	3.5		3.5
Tax benefit of exercised stock options allocated from Parent	15.8		15.8
Ending - Balance at Dec. 31, 2014	$3,412.80	$332.90	$984.40	$2,095.50

Acquisition_Notes

Acquisition (Notes)	12 Months Ended
	Dec. 31, 2014
Acquisition [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	PROPOSED ACQUISITION OF INTEGRYS BY WISCONSIN ENERGY
	On June 22, 2014, our parent company, Wisconsin Energy, entered into an agreement and plan of merger (Merger Agreement) under which it will acquire Integrys Energy Group (Integrys). Integrys' shareholders will receive 1.128 shares of Wisconsin Energy common stock and $18.58 in cash per Integrys share of common stock. We expect Wisconsin Energy to finance the acquisition through the issuance of approximately 91 million shares of Wisconsin Energy common stock to Integrys shareholders and through the issuance of approximately $1.5 billion of debt. Wisconsin Energy will also assume all of Integrys' outstanding debt. The combined company will be named WEC Energy Group, Inc.
	The acquisition is subject to several conditions, including, among others, approval of the shareholders of both Wisconsin Energy and Integrys, the expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (HSR Act), and the receipt of approvals from various government agencies, including the FERC, Federal Communications Commission, PSCW, Illinois Commerce Commission, MPSC and Minnesota Public Utilities Commission. The status of these matters as of December 31, 2014 is as follows:
	•	On August 6, 2014, Wisconsin Energy filed applications for approval with the PSCW, Illinois Commerce Commission, MPSC and Minnesota Public Utilities Commission.
	•	On August 15, 2014, Wisconsin Energy filed an application with the FERC. The initial public comment period closed on October 17, 2014. Wisconsin Energy subsequently submitted additional information to respond to FERC questions on December 18, 2014. That comment period is now closed.
	•	On September 24, 2014, Wisconsin Energy submitted its HSR Act filings, and on October 24, 2014, the United States Department of Justice closed its review of the transaction with no further action required. In addition, on October 24, 2014, the Federal Trade Commission granted early termination of the 30-day waiting period required by the HSR Act.
	•	On November 21, 2014, the shareholders of Wisconsin Energy voted to approve the issuance of common stock as contemplated by the Merger Agreement, as well as to amend the restated articles of incorporation to change the name of Wisconsin Energy from Wisconsin Energy Corporation to WEC Energy Group, Inc. The shareholders of Integrys approved the adoption of the Merger Agreement at its shareholder meeting held on November 21, 2014.
	Wisconsin Energy anticipates the transaction closing in the second half of 2015.

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation [Abstract]
ASSET RETIREMENT OBLIGATIONS	ASSET RETIREMENT OBLIGATIONS
	AROs have been recorded for asbestos abatement at certain generation and substation facilities, and for obligations associated with the removal and dismantlement of generation facilities. AROs are recorded in other long-term liabilities on the Consolidated Balance Sheets. The following table presents the change in our AROs during 2014 and 2013:
		2014			2013
		(Millions of Dollars)
	Balance as of January 1	$	39.4		$	41.5
	Liabilities Settled	(1.1		)	(4.3		)
	Accretion	2.2			2.2
	Balance as of December 31	$	40.5		$	39.4

Benefits

Benefits	12 Months Ended
	Dec. 31, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]
BENEFITS	BENEFITS
	Pensions and Other Post-retirement Benefits:   We participate in Wisconsin Energy's defined benefit pension plans that cover substantially all of our employees. Generally, employees who started with the Company after 1995 receive a benefit based on a percentage of their annual salary plus an interest credit, while employees who started before 1996 receive a benefit based upon years of service and final average salary. Approximately half of our projected benefit obligation relates to benefits based upon years of service and final average salary. New management employees hired after December 31, 2014 will receive a 6% annual Company contribution to their 401(k) plan instead of being enrolled in the defined benefit plans.
	We also participate in Wisconsin Energy's OPEB plans that cover substantially all of our employees. The health care plans are contributory with participants' contributions adjusted annually; the life insurance plans are noncontributory. The accounting for the health care plans anticipates future cost-sharing changes to the written plans that are consistent with our expressed intent to maintain the current cost sharing levels. The post-retirement health care plans include a limit on our share of costs for recent and future retirees.
	The assets, obligations and the components of our pension costs are allocated by Wisconsin Energy's actuary to each of the participating companies as if each participating company had its own plan. The disclosures below are based on an allocation to us of the amounts for Wisconsin Energy's pension plans.
	We use a year-end measurement date to measure the funded status of all of the pension and OPEB plans. Due to the regulated nature of our business, we have concluded that substantially all of the unrecognized costs resulting from the recognition of the funded status of the pension and OPEB plans qualify as a regulatory asset.
	The following table presents details about the pension and OPEB plans:
			Pension						OPEB
			2014			2013			2014			2013
			(Millions of Dollars)
	Change in Benefit Obligation
	Benefit Obligation at January 1		$	1,223.10		$	1,310.30		$	292.4		$	305.4
	Service cost		9.4			13.9			8.1			9.5
	Interest cost		59.3			52.4			14.4			12.7
	Participants' contributions		—			—			8.4			8.1
	Plan amendments		—			(0.9		)	(5.2		)	—
	Actuarial loss (gain)		110.8			(73.9		)	24.3			(22.7		)
	Other accrued benefits		(0.1		)	—			—			—
	Gross benefits paid		(87.3		)	(78.7		)	(21.1		)	(21.3		)
	Federal subsidy on benefits paid		N/A			N/A			1			0.7
	Benefit Obligation at December 31		$	1,315.20		$	1,223.10		$	322.3		$	292.4
	Change in Plan Assets
	Fair Value at January 1		$	1,168.90		$	1,121.10		$	222.4		$	194.8
	Actual earnings on plan assets		71.2			119			12			30.7
	Employer contributions		7.2			7.5			3.2			10.1
	Participants' contributions		—			—			8.4			8.1
	Gross benefits paid		(87.3		)	(78.7		)	(21.1		)	(21.3		)
	Fair Value at December 31		$	1,160.00		$	1,168.90		$	224.9		$	222.4
	Net liability		$	155.2		$	54.2		$	97.4		$	70
	Amounts recognized in our Consolidated Balance Sheets as of December 31 related to the funded status of the benefit plans consisted of:
			Pension						OPEB
			2014			2013			2014			2013
			(Millions of Dollars)
	Other long-term assets		$	—		$	34.3		$	1.9		$	1.6
	Other long-term liabilities		$	155.2		$	88.5		$	99.3		$	71.6
	Net liability		$	155.2		$	54.2		$	97.4		$	70
	The accumulated benefit obligation for all defined benefit plans was $1,314.3 million and $1,222.3 million as of December 31, 2014 and 2013, respectively.
	The following table shows the amounts that have not yet been recognized in our net periodic benefit cost as of December 31 and are recorded as a regulatory asset on our balance sheet:
			Pension						OPEB
			2014			2013			2014			2013
			(Millions of Dollars)
	Net actuarial loss (gain)		$	476.4		$	384.7		$	20.7		$	(7.6	)
	Prior service costs (credits)		6.3			8.3			(5.2		)	(1.7		)
	Total - Regulatory Assets (Liabilities)		$	482.7		$	393		$	15.5		$	(9.3	)
	We estimate that 2015 periodic pension and OPEB costs will include the amortization of previously unrecognized benefit costs (credits) referred to above of $38.0 million and $(0.2) million, respectively.
	The components of net periodic pension and OPEB costs for the years ended December 31 are as follows:
			Pension									OPEB
			2014			2013			2012			2014			2013			2012
			(Millions of Dollars)
	Net Periodic Benefit Cost
	Service cost		$	9.4		$	13.9		$	19.8		$	8.1		$	9.5		$	9.8
	Interest cost		59.3			52.4			56.8			14.4			12.7			16.7
	Expected return on plan assets		(79.1		)	(77.2		)	(71.8		)	(16.2		)	(14.5		)	(13.0		)
	Amortization of:
	Transition obligation		—			—			—			—			—			0.3
	Prior service cost (credit)		2			2.2			2.1			(1.7		)	(1.9		)	(1.9		)
	Actuarial loss		26.9			41.7			30.6			0.2			1.5			5
	Settlement charge		—			1.5			—			—			—			—
	Other		—			—			0.4			—			—			—
	Net Periodic Benefit Cost		$	18.5		$	34.5		$	37.9		$	4.8		$	7.3		$	16.9
			Pension					OPEB
			2014		2013	2012		2014	2013		2012
	Weighted-Average assumptions used to
	determine benefit obligations as of Dec. 31
	Discount rate		4.15%		5.00%	4.10%		4.20%	4.95%		4.15%
Rate of compensation increase		4.00%		4.00%	4.00%		N/A	N/A		N/A
Weighted-Average assumptions used to
determine net cost for year ended Dec. 31
Discount rate		5.00%		4.10%	5.05%		4.95%	4.15%		5.20%
Expected return on plan assets		7.25%		7.25%	7.25%		7.50%	7.50%		7.50%
Rate of compensation increase		4.00%		4.00%	4.00%		N/A	N/A		N/A
Assumed health care cost trend rates as of Dec. 31
Health care cost trend rate assumed for next year (Pre 65 / Post 65)							7.5%/7.5%	7.5%/7.5%		7.5%/7.5%
Rate that the cost trend rate gradually adjusts to							5.00%	5.00%		5.00%
Year that the rate reaches the rate it is assumed to remain at (Pre 65 / Post 65)							2021/2021	2021/2021		2017/2017
The expected long-term rate of return on pension and OPEB plan assets was 7.25% and 7.50%, respectively, in 2014, 2013 and 2012. Wisconsin Energy consults with its investment advisors on an annual basis to help forecast expected long-term returns on plan assets by reviewing historical returns as well as calculating expected total trust returns using the weighted-average of long-term market returns for each of the major target asset categories utilized in the fund.
A one-percentage-point change in assumed health care cost trend rates would have the following effects:
		1% Increase			1% Decrease
		(Millions of Dollars)
Effect on
Post-retirement benefit obligation		$	29.3		$	(24.4	)
Total of service and interest cost components		$	3.1		$	(2.5	)
We use various Employees' Benefit Trusts to fund a major portion of OPEB. The majority of the trusts' assets are mutual funds.
Plan Assets:   Current pension trust assets and amounts which are expected to be contributed to the trusts in the future are expected to be adequate to meet pension payment obligations to current and future retirees.
The Investment Trust Policy Committee oversees investment matters related to all of our funded benefit plans. The Committee works with external actuaries and investment consultants on an on-going basis to establish and monitor investment strategies and target asset allocations. Forecasted cash flows for plan liabilities are regularly updated based on annual valuation results. Target allocations are determined utilizing projected benefit payment cash flows and risk analyses of appropriate investments. They are intended to reduce risk, provide long-term financial stability for the plans and maintain funded levels which meet long-term plan obligations while preserving sufficient liquidity for near-term benefit payments.
Previously, our pension plan target allocation was 45% equity investments and 55% fixed income investments. In late 2014, we began transitioning to a target asset allocation of 35% equity investments, 55% fixed income investments and 10% private equity and real estate investments. The current OPEB target asset allocation is 60% equity investments and 40% fixed income investments. Equity securities include investments in large-cap, mid-cap and small-cap companies primarily located in the United States. Fixed income securities include corporate bonds of companies from diversified industries, mortgage and other asset backed securities, commercial paper, and U.S. Treasuries.
The following table summarizes the fair value of our share of plan assets by asset category within the fair value hierarchy (for further level information, see Note M):
		As of December 31, 2014
Asset Category - Pension		Level 1			Level 2			Level 3			Total
		(Millions of Dollars)
Cash and Cash Equivalents		$	5.1		$	—		$	—		$	5.1
Equities:
U.S. Equity		404.5			—			—			404.5
International Equity		103.3			23.9			—			127.2
Fixed Income:
Short, Intermediate and Long-term Bonds (a)
U.S. Bonds		34.2			481.2			—			515.4
International Bonds		63.7			34.8			—			98.5
Private equity and real estate		—			—			9.3			9.3
Total		$	610.8		$	539.9		$	9.3		$	1,160.00
		As of December 31, 2013
Asset Category - Pension		Level 1			Level 2			Level 3			Total
		(Millions of Dollars)
Cash and Cash Equivalents		$	16.9		$	—		$	—		$	16.9
Equities:
U.S. Equity		418.5			—			—			418.5
International Equity		117.8			28.8			—			146.6
Fixed Income:
Short, Intermediate and Long-term Bonds (a)
U.S. Bonds		87.3			407			—			494.3
International Bonds		62.9			29.7			—			92.6
Total		$	703.4		$	465.5		$	—		$	1,168.90
(a)	This category represents investment grade bonds of U.S. and foreign issuers denominated in U.S. dollars from diverse industries.
The following table summarizes the fair value of our share of OPEB plan assets by asset category within the fair value hierarchy:
		As of December 31, 2014
Asset Category - OPEB		Level 1			Level 2			Level 3			Total
		(Millions of Dollars)
Cash and Cash Equivalents		$	0.9		$	—		$	—		$	0.9
Equities:
U.S. Equity		98.4			—			—			98.4
International Equity		28.5			1.7			—			30.2
Fixed Income:
Short, Intermediate and Long-term Bonds (a)
U.S. Bonds		2.4			75.8			—			78.2
International Bonds		11.8			4.7			—			16.5
Private equity and real estate		—			—			0.7			0.7
Total		$	142		$	82.2		$	0.7		$	224.9
		As of December 31, 2013
Asset Category - OPEB		Level 1			Level 2			Level 3			Total
		(Millions of Dollars)
Cash and Cash Equivalents		$	1.8		$	—		$	—		$	1.8
Equities:
U.S. Equity		100.5			—			—			100.5
International Equity		31.8			1.9			—			33.7
Fixed Income:
Short, Intermediate and Long-term Bonds (a)
U.S. Bonds		5.7			65.4			—			71.1
International Bonds		11.4			3.9			—			15.3
Total		$	151.2		$	71.2		$	—		$	222.4
(a)	This category represents investment grade bonds of U.S. and foreign issuers denominated in U.S. dollars from diverse industries.
In December 2014, our pension and OPEB plans began investing in private equity funds which are a Level 3 investment.
Cash Flows:
Historical employer contributions:
		Pension
Year		Qualified			Non-Qualified			OPEB
		(Millions of Dollars)
2012		$	88.5		$	6		$	13.6
2013		$	—		$	7.5		$	10.1
2014		$	—		$	7.2		$	3.2
In January 2015, we contributed $100.0 million to the qualified pension plan. Future contributions to the plans will be dependent upon many factors, including the performance of plan assets, long-term discount rates and mortality rates.
Estimated benefit payments:
Year		Pension			Gross OPEB
		(Millions of Dollars)
2015		$	91.8		$	13.9
2016		$	91.5		$	14.8
2017		$	92.1		$	16
2018		$	89.5		$	17.1
2019		$	89.4		$	18.2
2020-2024		$	429.5		$	99.3
Savings Plans:   We sponsor savings plans which allow employees to contribute a portion of their pre-tax and/or after-tax income in accordance with plan-specified guidelines. Under these plans, we expensed matching contributions of $13.0 million, $13.0 million and $12.5 million during 2014, 2013 and 2012, respectively.
Postemployment Benefits:   Postemployment benefits provided to former or inactive employees are recognized when an event occurs. The estimated liability for such benefits was $1.8 million and $2.8 million as of December 31, 2014 and 2013, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES
	Operating Leases:   We enter into long-term purchase power contracts to meet a portion of our anticipated increase in future electric energy supply needs. These contracts expire at various times through 2018. Certain of these contracts were deemed to qualify as operating leases. In addition, we have various other operating leases, including leases for coal cars.
	Future minimum payments for the next five years and thereafter for our operating lease contracts are as follows:
		(Millions of Dollars)
	2015	$	5.2
	2016	3.9
	2017	3.2
	2018	3.1
	2019	1.2
	Thereafter	21.5
	Total	$	38.1
	Divested Assets:   We provided customary indemnifications to Wisconsin Power and Light Company, a subsidiary of Alliant Energy Corporation, in connection with the sale of our interest in Edgewater Generating Unit 5.
	Environmental Matters:   We periodically review our exposure for environmental remediation costs as evidence becomes available indicating that our liability has changed. Given current information, including the following, we believe that future costs in excess of the amounts accrued and/or disclosed on all presently known and quantifiable environmental contingencies will not be material to our financial position or results of operations.
	We have a program of comprehensive environmental remediation planning for former manufactured gas plant sites and coal combustion product disposal sites. We perform ongoing assessments of our manufactured gas plant sites and related disposal sites, as well as our coal combustion product disposal/landfill sites. We are working with the WDNR in our investigation and remediation planning. At this time, we cannot estimate future remediation costs associated with these sites beyond those described below.
	Manufactured Gas Plant Sites:   We have identified several sites at which we or a predecessor company historically owned or operated a manufactured gas plant. These sites have been substantially remediated or are at various stages of investigation, monitoring and remediation. We have also identified other sites that may have been impacted by historical manufactured gas plant activities. Based upon on-going analysis, we estimate that the future costs for detailed site investigation and future remediation costs may range from $6 million to $12 million over the next ten years. This estimate is dependent upon several variables including, among other things, the extent of remediation, changes in technology and changes in regulation. As of December 31, 2014 and 2013, we established reserves of $6.5 million and $10.8 million, respectively, related to future remediation costs.
	Historically, the PSCW has allowed Wisconsin utilities, including us, to defer the costs spent on the remediation of manufactured gas plant sites, and has allowed for these costs to be recovered in rates over five years. Accordingly, we have recorded a regulatory asset for remediation costs.
	Coal Combustion Product Landfill Sites:   We aggressively seek environmentally acceptable, beneficial uses for our coal combustion products. However, some coal combustion products have been, and to a small degree continue to be, managed in company-owned, licensed landfills. Some early designed and constructed landfills have at times required various levels of monitoring or remediation. Where we have become aware of these conditions, efforts have been made to define the nature and extent of any release, and work has been performed to address these conditions. During 2014, 2013 and 2012, we incurred $0.1 million, $0.1 million and $0.3 million, respectively, in landfill remediation expenses. As of December 31, 2014, we have no reserves established related to coal combustion product landfill sites.
	Valley Power Plant Title V Air Permit:   The WDNR renewed VAPP's Title V operating permit in February 2011. The term of the permit is five years. In March 2011, the Sierra Club petitioned the EPA for additional reductions and monitoring for particulate matter and revisions to certain applicable requirements. No timeline has been set by the EPA to respond to that petition. In May 2012, the Sierra Club filed a notice of intent to bring suit to force the EPA to issue a response to that petition. We believe that the permit was properly issued and that the plant is in compliance with all applicable regulations and standards. However, if as a result of this proceeding the permit is remanded to the WDNR, the plant will continue to operate under the previous operating permit.

Common_Equity

Common Equity	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
COMMON EQUITY	COMMON EQUITY
	Share-Based Compensation Plans:   Our employees participate in a plan approved by Wisconsin Energy stockholders that provides a long-term incentive through equity interests in Wisconsin Energy to outside directors, selected officers and key employees of Wisconsin Energy and its subsidiaries. The plan provides for the granting of Wisconsin Energy stock options, stock appreciation rights, restricted stock awards and performance shares. Awards may be paid in Wisconsin Energy common stock, cash or a combination thereof. We utilize the straight-line attribution method for recognizing share-based compensation expense. Accordingly, for employee awards, equity classified share-based compensation cost is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period. There were no modifications to the terms of outstanding Wisconsin Energy stock options held by our employees during the period.
	The following table summarizes recorded pre-tax share-based compensation expense and the related tax benefit for Wisconsin Energy share-based awards made to our employees during the years ended December 31:
		2014			2013			2012
		(Millions of Dollars)
	Performance units	$	12.7		$	11.9		$	14.2
	Stock options	3.6			3.8			2.6
	Restricted stock	2.1			1.6			2
	Share-based compensation expense	$	18.4		$	17.3		$	18.8
	Related Tax Benefit	$	7.4		$	6.9		$	7.5
	Stock Options:   The exercise price of a Wisconsin Energy stock option under the plan is to be no less than 100% of the common stock's fair market value on the grant date and options may not be exercised within six months of the grant date except in the event of a change in control. Option grants consist of non-qualified stock options that vest on a cliff-basis after a three year period. Options expire no later than 10 years from the date of grant. For further information regarding stock-based compensation and the valuation of Wisconsin Energy stock options, see Note A.
	The following is a summary of Wisconsin Energy stock option activity by our employees during 2014:
							Weighted-Average
				Weighted-			Remaining		Aggregate
		Number of		Average			Contractual Life		Intrinsic Value
	Stock Options	Options		Exercise Price			(Years)		(Millions)
	Outstanding as of January 1, 2014	7,688,843		$	26.92
	Granted	864,860		$	41.03
	Exercised	(2,086,231	)	$	22.95
	Forfeited	(17,195	)	$	37.42
	Outstanding as of December 31, 2014	6,450,277		$	30.07		5.7		$	146.2
	Exercisable as of December 31, 2014	3,682,442		$	24.14		3.9		$	105.3
	We expect that substantially all of the outstanding options as of December 31, 2014 will be exercised.
	In January 2015, the Compensation Committee of the Board of Directors of Wisconsin Energy (Compensation Committee) awarded 495,550 Wisconsin Energy non-qualified stock options with an exercise price of $52.895 to our officers and other key employees under its normal schedule of awarding long-term incentive compensation.
	The intrinsic value of Wisconsin Energy options exercised during the years ended December 31, 2014, 2013 and 2012 was $47.5 million, $41.2 million and $42.9 million, respectively. Cash received by Wisconsin Energy from exercises of its options by our employees was $47.9 million, $45.5 million and $45.4 million during the years ended December 31, 2014, 2013 and 2012, respectively. The actual tax benefit realized for the tax deductions from option exercises for the same periods was approximately $18.8 million, $16.6 million and zero, respectively.
	The following table summarizes information about Wisconsin Energy stock options held by our employees and outstanding as of December 31, 2014:
		Options Outstanding					Options Exercisable
				Weighted-Average						Weighted-Average
						Remaining					Remaining
		Number of		Exercise		Contractual	Number of			Exercise	Contractual
	Range of Exercise Prices	Options		Price		Life (Years)	Options			Price	Life (Years)
	$17.10  to  $21.11	1,411,769		$20.88		3.6	1,411,769			$20.88	3.6
	$23.88  to  $29.35	2,038,633		$25.07		3.7	2,038,633			$25.07	3.7
	$34.88  to  $41.03	2,999,875		$37.79		8	232,040			$35.86	7.4
		6,450,277		$30.07		5.7	3,682,442			$24.14	3.9
	The following table summarizes information about non-vested Wisconsin Energy options held by our employees during 2014:
		Number of		Weighted-
				Average
	Non-Vested Stock Options	Options		Fair Value
	Non-Vested as of January 1, 2014	2,289,400		$3.38
	Granted	864,860		$4.18
	Vested	(369,230	)	$3.26
	Forfeited	(17,195	)	$3.56
	Non-Vested as of December 31, 2014	2,767,835		$3.65
	As of December 31, 2014, total compensation costs related to non-vested Wisconsin Energy stock options held by our employees and not yet recognized was approximately $2.0 million, which is expected to be recognized over the next 19 months on a weighted-average basis.
	Restricted Shares:   The Compensation Committee has also approved grants of Wisconsin Energy restricted stock to certain of our key employees. The following restricted stock activity related to our employees occurred during 2014:
		Number of		Weighted-
				Average
				Market
	Restricted Shares	Shares		Price
	Outstanding as of January 1, 2014	98,226
	Granted	51,873		$40.98
	Released	(46,228	)	$34.31
	Forfeited	(3,214	)	$38.47
	Outstanding as of December 31, 2014	100,657
	In January 2015, the Compensation Committee awarded 43,212 restricted shares to our officers and other key employees under its normal schedule of awarding long-term incentive compensation. These awards have a three-year vesting period, and one-third of the award vests on each anniversary of the grant date. During the vesting period, restricted share recipients also have voting rights and are entitled to dividends in the same manner as other shareholders.
	Wisconsin Energy records the market value of the restricted stock awards on the date of grant. We then amortize our share of allocated expense over the vesting period of the awards. The intrinsic value of Wisconsin Energy restricted stock vesting and held by our employees was $2.3 million, $2.8 million and $2.2 million for the years ended December 31, 2014, 2013 and 2012, respectively. The actual tax benefit realized for the tax deductions from released restricted shares for the same years was $0.9 million, $1.1 million and zero, respectively.
	As of December 31, 2014, total compensation cost related to our share of Wisconsin Energy restricted stock not yet recognized was approximately $2.1 million, which is expected to be recognized over the next 20 months on a weighted-average basis.
	Performance Units:   In January 2014, 2013 and 2012, the Compensation Committee awarded 224,735, 230,245 and 333,685 Wisconsin Energy performance units, respectively, to our officers and other key employees under the Wisconsin Energy Performance Unit Plan. Under the grants, the ultimate number of units that will be awarded is dependent upon the achievement of certain financial performance of Wisconsin Energy's common stock over a three-year period. Under the terms of the award, participants may earn between 0% and 175% of the base performance unit award. All grants are settled in cash. We are accruing our share of compensation costs over the three-year performance period based on our estimate of the final expected value of the awards. Performance units earned as of December 31, 2014, 2013 and 2012 vested and were settled during the first quarter of 2015, 2014 and 2013, and had a total intrinsic value of $11.6 million, $13.1 million and $17.1 million, respectively. The actual tax benefit realized for the tax deductions from the settlement of performance units was approximately $4.2 million, $4.7 million and $6.2 million, respectively. As of December 31, 2014, total compensation cost related to performance units not yet recognized was approximately $10.9 million, which is expected to be recognized over the next 20 months on a weighted-average basis.
	In January 2015, the Compensation Committee awarded 187,450 performance units to our officers and other key employees under its normal schedule of awarding long-term incentive compensation.
	Restrictions:   Various financing arrangements and regulatory requirements impose certain restrictions on our ability to transfer funds to Wisconsin Energy in the form of cash dividends, loans or advances. In addition, under Wisconsin law, we are prohibited from loaning funds, either directly or indirectly, to Wisconsin Energy.
	We are required to maintain a capital structure that differs from GAAP as it reflects regulatory adjustments. Both the 2013 PSCW rate case order and the 2015 PSCW rate case order require us to maintain a common equity ratio range of between 48.5% and 53.5%. We are in compliance with the common equity ratio range. We must obtain PSCW approval to pay dividends above the test year levels that would cause us to fall below the authorized level of common equity.
	We may not pay common dividends to Wisconsin Energy under our Restated Articles of Incorporation if any dividends on our outstanding preferred stock have not been paid. In addition, pursuant to the terms of our 3.60% Serial Preferred Stock, our ability to declare common dividends would be limited to 75% or 50% of net income during a twelve month period if our common stock equity to total capitalization, as defined in the preferred stock designation, is less than 25% and 20%, respectively.
	See Note K for discussion of certain financial covenants related to our bank back-up credit facility.
We do not believe that these restrictions will materially affect our operations or limit any dividend payments in the foreseeable future.

Derivative_Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedges, Assets [Abstract]
DERIVATIVE INSTRUMENTS	DERIVATIVE INSTRUMENTS
	We utilize derivatives as part of our risk management program to manage the volatility and costs of purchased power, generation and natural gas purchases for the benefit of our customers. Our approach is non-speculative and designed to mitigate risk and protect against price volatility. Regulated hedging programs require prior approval by the PSCW.
	We record derivative instruments on the balance sheet as an asset or liability measured at its fair value, and changes in the derivative's fair value are recognized currently in earnings unless specific hedge accounting criteria are met or we receive regulatory treatment for the derivative. For most energy related physical and financial contracts in our regulated operations that qualify as derivatives, the PSCW allows the effects of the fair market value accounting to be offset to regulatory assets and liabilities. As of December 31, 2014, we recognized $8.4 million in regulatory assets and $12.2 million in regulatory liabilities related to derivatives in comparison to $0.3 million in regulatory assets and $8.1 million in regulatory liabilities as of December 31, 2013.
	We record our current derivative assets on the balance sheet in other current assets and the current portion of the liabilities in other current liabilities. The long-term portion of our derivative assets of $0.6 million is recorded in other deferred charges and other assets as of December 31, 2014, and the long-term portion of derivative liabilities of $0.7 million is recorded in other deferred credit and other liabilities as of December 31, 2014. Our Consolidated Balance Sheets as of December 31, 2014 and 2013 include:
			December 31, 2014								December 31, 2013
			Derivative				Derivative				Derivative				Derivative
			Asset				Liability				Asset				Liability
			(Millions of Dollars)
	Natural Gas		$	2.3			$	7.1			$	2.8			$	0.1
	Fuel Oil		—				—				0.6				—
	FTRs		7				—				3.5				—
	Coal		3.3				0.2				2.1				0.2
	Total		$	12.6			$	7.3			$	9			$	0.3
	Our Consolidated Income Statements include gains (losses) on derivative instruments used in our risk management strategies under fuel and purchased power for those commodities supporting our electric operations and under cost of gas sold for the natural gas sold to our customers. Our estimated notional volumes and gains (losses) for the years ended December 31, 2014 and 2013 were as follows:
			2014						2013
			Volume		Gains				Volume		Gains (Losses)
					(Millions of Dollars)						(Millions of Dollars)
	Natural Gas		21.4 million Dth		$	4			24.0 million Dth		$	(4.0	)
	Fuel Oil		9.2 million gallons		0.5				8.6 million gallons		0.5
	FTRs		26.1 million MWh		12.7				25.3 million MWh		14.9
	Total				$	17.2					$	11.4
	As of December 31, 2014 and 2013, we posted collateral of $6.9 million and zero, respectively, in our margin accounts. These amounts are recorded on the balance sheets in other current assets.
	The fair value amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral are not offset against the fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement. The table below shows derivative assets and derivative liabilities if derivative instruments by counterparty were presented net on the balance sheet as of December 31, 2014 and 2013.
		December 31, 2014								December 31, 2013
		Derivative				Derivative				Derivative				Derivative
		Asset				Liability				Asset				Liability
		(Millions of Dollars)
	Gross Amount Recognized on the Balance Sheet	$	12.6			$	7.3			$	9			$	0.3
	Gross Amount Not Offset on Balance Sheet (a)	(0.4		)		(6.8		)		—				—
	Net Amount	$	12.2			$	0.5			$	9			$	0.3
	(a)	Gross Amount Not Offset on Balance Sheet includes cash collateral posted of $6.4 million and zero as of December 31, 2014 and 2013, respectively.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS
	Fair value measurements require enhanced disclosures about assets and liabilities that are measured and reported at fair value and establish a hierarchal disclosure framework which prioritizes and ranks the level of observable inputs used in measuring fair value.
	Fair value is the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). We primarily apply the market approach for recurring fair value measurements and attempt to utilize the best available information. Accordingly, we also utilize valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. We are able to classify fair value balances based on the observability of those inputs. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3).
	Assets and liabilities measured and reported at fair value are classified and disclosed in one of the following categories:
	Level 1 -- Pricing inputs are unadjusted quoted prices available in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Instruments in this category consist of financial instruments such as exchange-traded derivatives, cash equivalents and restricted cash investments.
	Level 2 -- Pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. Instruments in this category include non-exchange-traded derivatives such as OTC forwards and options.
	Level 3 -- Pricing inputs include significant inputs that are generally less observable from objective sources. The inputs in the determination of fair value require significant management judgment or estimation. At each balance sheet date, we perform an analysis of all instruments subject to fair value reporting and include in Level 3 all instruments whose fair value is based on significant unobservable inputs.
	In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, an instrument's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the instrument.
	The following tables summarize our financial assets and liabilities by level within the fair value hierarchy:
	Recurring Fair Value Measures	As of December 31, 2014
		Level 1			Level 2			Level 3		Total
		(Millions of Dollars)
	Assets:
	Derivatives	$	0.4		$	5.2		$	7	$	12.6
	Total	$	0.4		$	5.2		$	7	$	12.6
	Liabilities:
	Derivatives	$	6.8		$	0.5		$	—	$	7.3
	Total	$	6.8		$	0.5		$	—	$	7.3
	Recurring Fair Value Measures	As of December 31, 2013
		Level 1			Level 2			Level 3		Total
		(Millions of Dollars)
	Assets:
	Derivatives	$	3.2		$	2.3		$	3.5	$	9
	Total	$	3.2		$	2.3		$	3.5	$	9
	Liabilities:
	Derivatives	$	—		$	0.3		$	—	$	0.3
	Total	$	—		$	0.3		$	—	$	0.3
	Derivatives reflect positions we hold in exchange-traded derivative contracts and OTC derivative contracts. Exchange-traded derivative contracts, which include futures and exchange-traded options, are generally based on unadjusted quoted prices in active markets and are classified within Level 1. Some OTC derivative contracts are valued using broker or dealer quotations, or market transactions in either the listed or OTC markets utilizing a mid-market pricing convention (the mid-point between bid and ask prices), as appropriate. In such cases, these derivatives are classified within Level 2. Certain OTC derivatives may utilize models to measure fair value. Generally, we use a similar model to value similar instruments. Valuation models utilize various inputs which include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, other observable inputs for the asset or liability, and market-corroborated inputs (i.e., inputs derived principally from or corroborated by observable market data by correlation or other means). Where observable inputs are available for substantially the full term of the asset or liability, the instrument is categorized in Level 2. Certain OTC derivatives are in less active markets with a lower availability of pricing information which might not be observable in or corroborated by the market. When such inputs have a significant impact on the measurement of fair value, the instrument is categorized in Level 3.
	The following table summarizes the changes to derivatives classified as Level 3 in the fair value hierarchy:
		2014			2013
		(Millions of Dollars)
	Balance as of January 1	$	3.5		$	4.7
	Realized and unrealized gains (losses)	—			—
	Purchases	15.6			10.6
	Issuances	—			—
	Settlements	(12.1		)	(11.8		)
	Transfers in and/or out of Level 3	—			—
	Balance as of December 31	$	7		$	3.5
	Derivative instruments reflected in Level 3 of the hierarchy include MISO FTRs that are measured at fair value each reporting period using monthly or annual auction shadow prices from relevant auctions. Changes in fair value for Level 3 recurring items are recorded on our balance sheet. See Note L -- Derivative Instruments for further information on the offset to regulatory assets and liabilities.
	The carrying amount and estimated fair value of certain of our recorded financial instruments as of December 31 are as follows:
		2014						2013
		Carrying			Fair			Carrying		Fair
	Financial Instruments	Amount			Value			Amount		Value
		(Millions of Dollars)
	Preferred stock, no redemption required	$	30.4		$	27.1		$	30.4	$	26
	Long-term debt including current portion	$	2,437.00		$	2,759.60		$	2,487.00	$	2,634.70
	The carrying value of net accounts receivable, accounts payable and short-term borrowings approximates fair value due to the short-term nature of these instruments. The fair value of our preferred stock is estimated based upon the quoted market value for the same or similar issues. The fair value of our long-term debt, including the current portion of long-term debt, but excluding capitalized leases and unamortized discount on debt, is estimated based upon quoted market value for the same or similar issues or upon the quoted market prices of U.S. Treasury issues having a similar term to maturity, adjusted for the issuing company's bond rating and the present value of future cash flows.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES
	The following table is a summary of income tax expense for each of the years ended December 31:
	Income Taxes		2014				2013				2012
			(Millions of Dollars)
	Current tax expense (benefit)		$	31.2			$	7.3			$	(1.4	)
	Deferred income taxes, net		192.5				194.7				195.2
	Investment tax credit, net		(1.1		)		(1.1		)		(1.1		)
	Total Income Tax Expense		$	222.6			$	200.9			$	192.7
	The provision for income taxes for each of the years ended December 31 differs from the amount of income tax determined by applying the applicable U.S. statutory federal income tax rate to income before income taxes and preferred dividend as a result of the following:
			2014							2013						2012
							Effective							Effective					Effective
	Income Tax Expense		Amount				Tax Rate			Amount				Tax Rate		Amount			Tax Rate
			(Millions of Dollars)
	Expected tax at statutory federal tax rates		$	209.8			35	%		$	196.3			35	%	$	195.6		35	%
	State income taxes net of federal tax benefit		33				5.5	%		31.7				5.6	%	28.8			5.1	%
	Production tax credits		(17.4		)		(2.9	)%		(16.7		)		(3.0	)%	(15.9		)	(2.8	)%
	Treasury Grant		(3.8		)		(0.6	)%		(7.4		)		(1.3	)%	—			—	%
	AFUDC - Equity		(1.5		)		(0.2	)%		(6.1		)		(1.1	)%	(12.2		)	(2.2	)%
	Investment tax credit restored		(1.1		)		(0.2	)%		(1.1		)		(0.2	)%	(1.1		)	(0.2	)%
	Domestic production activities deduction		—				—	%		—				—	%	(12.6		)	(2.3	)%
	Other, net		3.6				0.5	%		4.2				0.7	%	10.1			1.8	%
	Total Income Tax Expense		$	222.6			37.1	%		$	200.9			35.7	%	$	192.7		34.4	%
	The components of deferred income taxes classified as net current assets and net long-term liabilities as of December 31 are as follows:
	Deferred Tax Assets		2014				2013
			(Millions of Dollars)
	Current
	Future federal tax benefits		$	56			$	113.1
	Uncollectible account expense		15.6				17.2
	Employee benefits and compensation		11.6				11.7
	Recoverable gas costs		1				0.5
	Other		2.3				3.3
	Total Current Deferred Tax Assets		86.5				145.8
	Non-current
	Deferred revenues		221.3				237
	Employee benefits and compensation		92.1				92.4
	Construction advances		15.5				15
	Emission Allowances		0.1				—
	Other		31.7				42.2
	Total Non-Current Deferred Tax Assets		360.7				386.6
	Total Deferred Tax Assets		$	447.2			$	532.4
	Deferred Tax Liabilities		2014				2013
			(Millions of Dollars)
	Current
	Prepaid items		$	39.8			$	70
	Total Current Deferred Tax Liabilities		39.8				70
	Non-current
	Property-related		1,942.20				1,820.90
	Investment in transmission affiliate		164.1				147.8
	Employee benefits and compensation		131.2				135
	Deferred transmission costs		58.5				50.8
	Other		28.6				26.6
	Total Non-current Deferred Tax Liabilities		2,324.60				2,181.10
	Total Deferred Tax Liabilities		$	2,364.40			$	2,251.10
	Consolidated Balance Sheet Presentation		2014				2013
	Current Deferred Tax Asset		$	46.7			$	75.8
	Non-Current Deferred Tax Liability		$	1,963.90			$	1,794.50
	Consistent with rate-making treatment, deferred taxes are offset in the above table for temporary differences which have related regulatory assets or liabilities.
	As of December 31, 2014, we had approximately $3.9 million and $54.6 million of net operating loss and tax credit carryforwards resulting in deferred tax assets of approximately $1.4 million and $54.6 million, respectively. As of December 31, 2013, we had approximately $216.8 million and $37.2 million of net operating loss and tax credit carryforwards resulting in deferred tax assets of approximately $75.9 million and $37.2 million, respectively. These net operating loss carryforwards begin to expire in 2030. We anticipate that we will have future taxable income sufficient to utilize these deferred tax assets.
	We previously adopted accounting guidance related to uncertainty in income taxes. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:
		2014				2013
		(Millions of Dollars)
	Balance as of January 1	$	8.4			$	10.8
	Reductions for tax positions of prior years	(1.2		)		(2.4		)
	Balance as of December 31	$	7.2			$	8.4
The amount of unrecognized tax benefits as of December 31, 2014 and 2013 excludes deferred tax assets related to uncertainty in income taxes of $7.2 million and $8.4 million, respectively. As of December 31, 2014 and 2013, there were no unrecognized tax benefits that, if recognized, would impact the effective tax rate for continuing operations.
We recognize interest and penalties accrued related to unrecognized tax benefits as a component of income tax expense. For the years ended December 31, 2014, 2013 and 2012, we recognized approximately $0.3 million, $0.2 million and $0.2 million, respectively, of accrued interest in the Consolidated Income Statements. For the years ended December 31, 2014, 2013 and 2012, we recognized no penalties in the Consolidated Income Statements. We had approximately $0.7 million and $0.4 million of interest accrued and no penalties accrued on the Consolidated Balance Sheets as of December 31, 2014 and 2013, respectively.
We do not anticipate any significant increases or decreases in the total amounts of unrecognized tax benefits within the next 12 months.
Our primary tax jurisdictions include the United States and the state of Wisconsin. Currently, the tax years of 2011 through 2014 are subject to Federal examination, and the tax years 2010 through 2014 are subject to examination by the state of Wisconsin.

LongTerm_Debt_and_Capital_Leas

Long-Term Debt and Capital Lease Obligations	12 Months Ended
	Dec. 31, 2014
Long-term Debt and Capital Lease Obligations [Abstract]
LONG-TERM DEBT AND CAPITAL LEASE OBLIGATIONS	LONG-TERM DEBT AND CAPITAL LEASE OBLIGATIONS
	Debentures and Notes:   As of December 31, 2014, the maturities of our long-term debt outstanding (excluding obligations under capital leases) were as follows:
		(Millions of Dollars)
	2015	$	250
	2016	—
	2017	—
	2018	250
	2019	250
	Thereafter	1,687.00
	Total	$	2,437.00
	We amortize debt premiums, discounts and debt issuance costs over the lives of the debt and we include the costs in interest expense.
	We are the obligor under two series of tax-exempt pollution control refunding bonds in outstanding principal amount of $147.0 million. In August 2009, we terminated letters of credit that provided credit and liquidity support for the bonds, which resulted in a mandatory tender of the bonds. We purchased the bonds at par plus accrued interest to the date of purchase. As of December 31, 2014 and 2013, the repurchased bonds were still outstanding, but were not reported in our consolidated long-term debt or included on our Consolidated Statements of Capitalization because they are held by us. Depending on market conditions and other factors, we may change the method used to determine the interest rate on the bonds and have them remarketed to third parties.
	Obligations Under Capital Leases
	We are the obligor under a power purchase contract with an unaffiliated third party and we lease power plants from We Power under Wisconsin Energy's PTF strategy. Under capital lease accounting, we have recorded the leased plants and corresponding obligations under the capital leases on our Consolidated Balance Sheets. We treat these agreements as operating leases for rate-making purposes. We record our minimum lease payments under the power purchase contract as purchased power expense on the Consolidated Income Statements. We record the lease payments under our PTF leases as rent expense in other operation and maintenance in the Consolidated Income Statements. We record the difference between the minimum lease payments and the sum of imputed interest and amortization costs calculated under capital lease accounting as a deferred regulatory asset on our Consolidated Balance Sheets (see Regulatory Assets - Deferred plant related -- capital leases in Note C).
	Power Purchase Commitment:   In 1997, we entered into a 25-year power purchase contract with an unaffiliated independent power producer. The contract, for 236 MW of firm capacity from a gas-fired cogeneration facility, includes no minimum energy requirements. When the contract expires in 2022, we may, at our option and with proper notice, renew for another ten years or purchase the generating facility at fair value or allow the contract to expire. We recorded the leased facility and corresponding obligation under the capital lease at the estimated fair value of the plant's electric generating facilities. We are amortizing the leased facility on a straight-line basis over the original 25-year term of the contract.
	PWGS:   We are leasing PWGS 1 and PWGS 2, two 545 MW natural gas-fired generation units which were placed in service in July 2005 and May 2008, respectively, from We Power under PSCW approved leases. The leased plants and corresponding obligations for the plants have been recorded at the estimated fair value of $682.7 million. We are amortizing the leased plants on a straight-line basis over the original 25-year term of the leases. The lease payments are expected to be recovered through our rates, as supported by the 2001 leased generation law. Due to the timing and the amounts of the minimum lease payments, we expect the regulatory asset to increase to approximately $129.1 million in the year 2021 for PWGS 1 and to approximately $127.9 million in the year 2024 for PWGS 2, at which time the regulatory assets will be reduced to zero over the remaining lives of the contracts. The total obligation under the capital leases for the plants was $637.1 million as of December 31, 2014, and will decrease to zero over the remaining lives of the contracts.
	Oak Creek Expansion:   We are leasing OC 1, OC 2 and the common facilities, which are also utilized by our Oak Creek Units 5-8, from We Power under PSCW approved leases. We are amortizing the leased plants on a straight-line basis over the 30-year term of the leases. OC 1 and OC 2 were placed in service in February 2010 and January 2011, respectively. The leased plants and corresponding capital lease obligations have been recorded at the estimated fair value of $2,025.6 million. The lease payments are expected to be recovered through our rates, as supported by the 2001 leased generation law. Due to the timing and the amounts of the minimum lease payments, we expect the regulatory asset to increase to approximately $537.6 million in the year 2029 for OC 1 and to approximately $442.0 million in the year 2030 for OC2, at which time the regulatory assets will be reduced to zero over the remaining lives of the contracts. The total obligation under the capital leases was $2,096.5 million as of December 31, 2014, and will decrease to zero over the remaining life of the contracts.
	We paid the following lease payments during 2014, 2013 and 2012:
			2014			2013			2012
			(Millions of Dollars)
	Long-term power purchase commitment		$	34.9		$	33.7		$	32.5
	PWGS		99.2			99.1			99
	Oak Creek Expansion		277.8			274.9			269.3
	Total		$	411.9		$	407.7		$	400.8
	The following table summarizes our capitalized leased facilities as of December 31:
	Capital Lease Assets		2014			2013
			(Millions of Dollars)
	Long-term Power Purchase Commitment
	Under capital lease		$	140.3		$	140.3
	Accumulated amortization		(98.3		)	(92.5		)
	Total Long-term Power Purchase Commitment		$	42		$	47.8
	PWGS
	Under capital lease		$	682.7		$	681.5
	Accumulated amortization		(217.6		)	(190.1		)
	Total PWGS		$	465.1		$	491.4
	Oak Creek Expansion
	Under capital lease		$	2,025.60		$	1,991.10
	Accumulated amortization		(317.7		)	(251.3		)
	Total Oak Creek		$	1,707.90		$	1,739.80
	Total Leased Facilities		$	2,215.00		$	2,279.00
	Future minimum lease payments under our capital leases and the present value of our net minimum lease payments as of December 31, 2014 are as follows:
			Power
			Purchase						Oak Creek
	Capital Lease Obligations		Commitment			PWGS			Expansion			Total
			(Millions of Dollars)
	2015		$	43.5		$	99.3		$	296.4		$	439.2
	2016		45.1			99.3			311			455.4
	2017		13.9			99.3			311.4			424.6
	2018		14.7			99.3			311.4			425.4
	2019		15.5			99.3			311.4			426.2
	Thereafter		41.3			1,184.70			6,378.50			7,604.50
	Total Minimum Lease Payments		174			1,681.20			7,920.10			9,775.30
	Less:  Estimated Executory Costs		(54.7		)	—			—			(54.7		)
	Net Minimum Lease Payments		119.3			1,681.20			7,920.10			9,720.60
	Less:  Interest		(34.8		)	(1,044.1		)	(5,823.6		)	(6,902.5		)
	Present Value of Net
	Minimum Lease Payments		84.5			637.1			2,096.50			2,818.10
	Less:  Due Currently		(24.6		)	(10.2		)	(70.8		)	(105.6		)
	Total Capital Lease Obligations		$	59.9		$	626.9		$	2,025.70		$	2,712.50

Preferred_Stock_Notes

Preferred Stock (Notes)	12 Months Ended
	Dec. 31, 2014
Preferred Stock [Abstract]
Preferred Stock [Text Block]	PREFERRED STOCK
	The following table shows preferred stock authorized and outstanding at December 31, 2014 and 2013:
		Shares Authorized	Shares Outstanding	Redemption Price Per Share		Total
						(In Millions)
	$100 par value, Six Per Cent. Preferred Stock	45,000	44,498	—		$	4.4
	$100 par value, Serial Preferred Stock	2,286,500
	3.60% Series		260,000	$	101	26
	$25 par value, Serial Preferred Stock	5,000,000	—	—		—
	Total Preferred Stock					$	30.4

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENT ACCOUNTING PRONOUNCEMENTS	RECENT ACCOUNTING PRONOUNCEMENTS
	Revenue Recognition: In May 2014, the Financial Accounting Standards Board and the International Accounting Standards Board issued their joint revenue recognition standard Accounting Standards Update 2014-09, Revenue from Contracts with Customers. This guidance is effective for fiscal years and interim periods beginning after December 15, 2016, and can either be applied retrospectively or as a cumulative-effect adjustment as of the date of adoption. We are currently assessing the effects this guidance may have on our consolidated financial statements.

Regulatory_Assets_and_Liabilit

Regulatory Assets and Liabilities	12 Months Ended
	Dec. 31, 2014
Regulatory Assets and Liabilities Disclosure [Abstract]
REGULATORY ASSETS AND LIABILITIES	REGULATORY ASSETS AND LIABILITIES
	Our primary regulator, the PSCW, considers our regulatory assets and liabilities in two categories, escrowed and deferred. In escrow accounting we expense amounts that are included in rates. If actual costs exceed or are less than the amounts that are allowed in rates, the difference in cost is escrowed on the balance sheet as a regulatory asset or regulatory liability and the escrowed balance is considered in setting future rates. Under deferred cost accounting, we defer amounts to our balance sheet based upon orders or correspondence with our regulators. These deferred costs will be considered in future rate setting proceedings. As of December 31, 2014, we had $11.7 million of regulatory assets not earning a return and $115.1 million of regulatory assets earning a return based on short-term interest rates.
	In December 2014, the PSCW issued a rate order effective January 1, 2015 that, among other things, reaffirmed our accounting for the regulatory assets and liabilities identified below.
	Our regulatory assets and liabilities as of December 31 consist of:
		2014		2013
		(Millions of Dollars)
	Regulatory Assets
	Deferred plant related -- capital leases	$	603	$	512.5
	Deferred unrecognized pension costs	482.8		393
	Deferred income tax related	171.5		165.8
	Escrowed electric transmission costs	146		126.8
	Other, net	223.6		172.2
	Total regulatory assets	$	1,626.90	$	1,370.30
	Regulatory Liabilities
	Deferred cost of removal obligations	$	571.2	$	558.9
	Other, net	44.7		75.3
	Total regulatory liabilities	$	615.9	$	634.2
	Our rates allow us to recover and expense capital lease payments as they are due. We defer as a regulatory asset the difference between the capital lease expense recovered in rates and the expense that would result from the amortization of the leased asset and the imputed interest expense.

Related_Parties

Related Parties	12 Months Ended
	Dec. 31, 2014
Related Party Transaction, Due from (to) Related Party [Abstract]
RELATED PARTIES	RELATED PARTIES
	We provide to and receive from certain of our Wisconsin Energy affiliates managerial, financial, accounting, legal, data processing and other services in accordance with service agreements approved by the PSCW. In addition, we make lease payments to We Power for PWGS 1, PWGS 2, OC 1 and OC 2. We also receive and/or provide certain services to other associated companies in which we have, or Wisconsin Energy has, an equity investment.
	American Transmission Company LLC:   As of December 31, 2014, we have a 23.0% interest in ATC. We pay ATC for transmission and other related services it provides. In addition, we provide a variety of operational, maintenance and project management work for ATC, which is reimbursed to us by ATC. We are required to pay the cost of needed transmission infrastructure upgrades for new generation projects while projects are under construction. ATC reimburses us for these costs when new generation is placed in service.
	During the years ended December 31, 2014, 2013 and 2012, our equity in earnings and distributions received from ATC were as follows:
	Equity Investee	2014		2013		2012
		(Millions of Dollars)
	Equity in Earnings	$	57.9	$	60.2	$	57.6
	Distributions Received	$	50.5	$	47.8	$	46.1
	Summary financial information as of December 31 from the financial statements of ATC is as follows:
		2014		2013		2012
		(Millions of Dollars)
	Operating Revenues	$	635	$	626.3	$	603.3
	Operating Income	$	327.6	$	331.3	$	322.2
	Net Income	$	238.7	$	247.6	$	237.4
	Current Assets	$	66.4	$	80.7	$	63.1
	Non-Current Assets	$	3,728.70	$	3,509.50	$	3,274.70
	Current Liabilities	$	313.1	$	381.5	$	251.5
	Non-Current Liabilities	$	1,864.80	$	1,676.20	$	1,645.80
	We provided and received services from the following associated companies during 2014, 2013 and 2012:
	Company	2014		2013		2012
		(Millions of Dollars)
	Affiliate
	Services Provided
	We Power (excluding lease payments)	$	41.5	$	2.8	$	2.3
	Wisconsin Gas	$	81.7	$	83.4	$	78.7
	Wisconsin Energy	$	11.3	$	5.6	$	5.6
	Other	$	1.5	$	1.6	$	1.2
	Services Received
	We Power (including lease payments)	$	389	$	381.7	$	375.3
	Wisconsin Gas	$	20.6	$	23.6	$	16.6
	Wisconsin Energy	$	15.2	$	10.2	$	23.9
	Equity Investee - ATC
	Services Provided	$	8.1	$	9	$	8.2
	Services Received	$	231.4	$	234.2	$	222.7
	As of December 31, 2014 and 2013, our Consolidated Balance Sheets included receivable and payable balances with ATC as follows:
	Equity Investee	2014		2013
		(Millions of Dollars)
	Accounts Receivable
	Services provided	$	0.6	$	0.6
	Accounts Payable
	Services received	$	19.3	$	19.5

Segment_Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
SEGMENT REPORTING	SEGMENT REPORTING
	We are a subsidiary of Wisconsin Energy and have organized our reportable segments according to how we are currently regulated. Our reportable operating segments include electric, natural gas and steam utility segments. The accounting policies of the reportable operating segments are the same as those described in Note A.
	Our electric utility engages in the generation, distribution and sale of electric energy in southeastern (including metropolitan Milwaukee), east central and northern Wisconsin and in the Upper Peninsula of Michigan. Our natural gas utility is engaged in the purchase, distribution and sale of natural gas to retail customers and the transportation of customer-owned natural gas in three service areas in southeastern, east central and northern Wisconsin. Our steam utility produces, distributes and sells steam to space heating and processing customers in the Milwaukee, Wisconsin area.
	Total asset information is not provided for reportable segments because as an integrated electric, natural gas and steam utility, significant assets are not dedicated to a specific reportable segment. Reporting assets by segment would require arbitrary and potentially misleading allocations which may not necessarily reflect the assets that would be required for the operation of the reportable segments on a stand-alone basis.
	Summarized financial information concerning our reportable segments for each of the three years ended December 31, 2014 is shown in the following table:
			Reportable Segments
	Year Ended		Electric		Gas		Steam			Other (a)		Total
			(Millions of Dollars)
	December 31, 2014
	Operating Revenues (b)		$	3,401.10	$	614.2	$	44.1		$	—	$	4,059.40
	Depreciation and Amortization		$	261.5	$	30.5	$	3.7		$	—	$	295.7
	Operating Income (c)		$	565.6	$	77.2	$	7.6		$	—	$	650.4
	Equity in Earnings
	of Transmission Affiliate		$	57.9	$	—	$	—		$	—	$	57.9
	Capital Expenditures		$	470.2	$	67.9	$	2.8		$	—	$	540.9
	December 31, 2013
	Operating Revenues (b)		$	3,308.70	$	451.9	$	39.6		$	—	$	3,800.20
	Depreciation and Amortization		$	249.5	$	25.5	$	3.6		$	—	$	278.6
	Operating Income (Loss) (c)		$	533.2	$	69.8	$	2.9		$	—	$	605.9
	Equity in Earnings
	of Transmission Affiliate		$	60.2	$	—	$	—		$	—	$	60.2
	Capital Expenditures		$	438.5	$	57.8	$	10.6		$	—	$	506.9
	December 31, 2012
	Operating Revenues (b)		$	3,193.90	$	385.1	$	34.3		$	—	$	3,613.30
	Depreciation and Amortization		$	230.3	$	23.9	$	3.4		$	—	$	257.6
	Operating Income (c)		$	536.5	$	50	$	(3.2	)	$	—	$	583.3
	Equity in Earnings
	of Transmission Affiliate		$	57.6	$	—	$	—		$	—	$	57.6
	Capital Expenditures		$	524.9	$	50.8	$	—		$	0.1	$	575.8
	(a)	Other includes primarily non-utility property and investments, materials and supplies, deferred charges and other corporate items.
	(b)	We account for intersegment revenues at a tariff rate established by the PSCW. Intersegment revenues were not material.
	(c)	We evaluate operating income to manage our utility business. Equity in Earnings of Transmission Affiliate, Interest Expense and Income Taxes are not included in segment operating income.

ShortTerm_Debt

Short-Term Debt	12 Months Ended
	Dec. 31, 2014
Short-term Debt [Abstract]
SHORT-TERM DEBT	SHORT-TERM DEBT
	Our commercial paper balance and the corresponding weighted-average interest rate as of December 31 are shown in the following table:
		2014			2013
				Interest			Interest
		Balance		Rate	Balance		Rate
		(Millions of Dollars, except for percentages)
	Commercial paper	$306.80		0.25%	$174.50		0.22%
	The following information relates to commercial paper outstanding for the years ended December 31:
		2014			2013
		(Millions of Dollars, except for percentages)
	Maximum Commercial Paper Outstanding	$	401		$	354.5
	Average Commercial Paper Outstanding	$	179.5		$	98
	Weighted-Average Interest Rate	0.22		%	0.22		%
	We have entered into a bank back-up credit facility to maintain short-term credit liquidity which, among other terms, requires us to maintain, subject to certain exclusions, a minimum total funded debt to capitalization ratio of less than 65%.
	As of December 31, 2014, we had approximately $494.9 million of available, undrawn lines under our bank back-up credit facility and $306.8 million of commercial paper outstanding that was supported by the available lines of credit. In December 2014, we amended our credit facility to extend its expiration from December 2017 to December 2019. As of December 31, 2014, our subsidiary had a $22.4 million note payable to Wisconsin Energy with a weighted-average interest rate of 6.75%.
	Our bank back-up credit facility contains customary covenants, including certain limitations on our ability to sell assets. The credit facility also contains customary events of default, including payment defaults, material inaccuracy of representations and warranties, covenant defaults, bankruptcy proceedings, certain judgments, Employee Retirement Income Security Act of 1974 (ERISA) defaults and change of control.
	As of December 31, 2014, we were in compliance with all financial covenants.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	General:   Wisconsin Electric Power Company (Wisconsin Electric, the Company, our, us or we), a subsidiary of Wisconsin Energy, is an electric, gas and steam utility which services electric customers in Wisconsin and the Upper Peninsula of Michigan, gas customers in Wisconsin and steam customers in metropolitan Milwaukee, Wisconsin. We consolidate our wholly-owned subsidiary, Bostco. Bostco had total assets of $28.4 million and $29.1 million as of December 31, 2014 and 2013, respectively.
	All intercompany transactions and balances have been eliminated from the consolidated financial statements.
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of certain assets and liabilities and disclosure of contingent assets and liabilities at the date of financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Revenues:   We recognize energy revenues on the accrual basis and include estimated amounts for services rendered but not billed.
	Our retail electric rates in Wisconsin are established by the PSCW and include base amounts for fuel and purchased power costs. The electric fuel rules in Wisconsin allow us to defer, for subsequent rate recovery or refund, any under-collection or over-collection of fuel costs that are outside of the symmetrical fuel cost tolerance, which the PSCW set at plus or minus 2% of the approved fuel cost plan. The deferred under-collected amounts are subject to an excess revenues test.
	Our retail gas rates include monthly adjustments which permit the recovery or refund of actual purchased gas costs. We defer any difference between actual gas costs incurred (adjusted for a sharing mechanism) and costs recovered through rates as a current asset or liability. The deferred balance is returned to or recovered from customers at intervals throughout the year.
	Accounting for MISO Energy Transactions:    The MISO Energy Markets operate under both day-ahead and real-time markets. We record energy transactions in the MISO Energy Markets on a net basis for each hour.
	Other Income and Deductions, Net:   We recorded the following items in Other Income and Deductions, net for the years ended December 31:
	Other Income and Deductions, net		2014			2013			2012
			(Millions of Dollars)
	AFUDC - Equity		$	4.4		$	17.6		$	34.9
	Gain on Property Sales		4.3			0.8			0.3
	Other, net		—			(1.0		)	(2.9		)
	Total Other Income and Deductions, net		$	8.7		$	17.4		$	32.3
	Property and Depreciation:   We record property, plant and equipment at cost. Cost includes material, labor, overheads and capitalized interest. Utility property also includes AFUDC - Equity. Additions to and significant replacements of property are charged to property, plant and equipment at cost; minor items are charged to maintenance expense. The cost of depreciable utility property less salvage value is charged to accumulated depreciation when property is retired.
	Our utility depreciation rates are certified by the PSCW and MPSC and include estimates for salvage value and removal costs. Depreciation as a percent of average depreciable utility plant was 2.9% in 2014, 2013 and 2012.
	For assets other than our regulated assets and leased equipment, we accrue depreciation expense at straight-line rates over the estimated useful lives of the assets, or over the non-cancellable lease term for leased equipment.
	We collect in our rates amounts representing future removal costs for many assets that do not have an associated Asset Retirement Obligation (ARO). We record a regulatory liability on our balance sheet for the estimated amounts we have collected in rates for future removal costs less amounts we have spent in removal activities. This regulatory liability was $571.2 million as of December 31, 2014 and $558.9 million as of December 31, 2013.
	Allowance For Funds Used During Construction:   AFUDC is included in utility plant accounts and represents the cost of borrowed funds (AFUDC - Debt) used during plant construction, and a return on stockholders' capital (AFUDC - Equity) used for construction purposes. AFUDC - Debt is recorded as a reduction of interest expense and AFUDC - Equity is recorded in Other Income and Deductions, net.
	We recorded the following AFUDC for the years ended December 31:
			2014			2013			2012
			(Millions of Dollars)
	AFUDC - Debt		$	1.8		$	7.4		$	14.5
	AFUDC - Equity		$	4.4		$	17.6		$	34.9
	Materials, Supplies and Inventories:   Our inventory as of December 31 consists of:
	Materials, Supplies and Inventories		2014			2013
			(Millions of Dollars)
	Fossil Fuel		$	125.5		$	117.5
	Materials and Supplies		145			129.5
	Natural Gas in Storage		50			34
	Total		$	320.5		$	281
	Substantially all fossil fuel, materials and supplies and natural gas in storage inventories are recorded using the weighted-average cost method of accounting.
	Regulatory Accounting:   The economic effects of regulation can result in regulated companies recording costs that have been or are expected to be allowed in the rate-making process in a period different from the period in which the costs would be charged to expense by an unregulated enterprise. When this occurs, costs are deferred as regulatory assets on the balance sheet and expensed in the periods when they are reflected in rates. We defer regulatory assets pursuant to specific or generic orders issued by our regulators. Additionally, regulators can impose regulatory liabilities upon a regulated company for amounts previously collected from customers and for amounts that are expected to be refunded to customers. In general, regulatory assets are recovered in a period between one to eight years. For further information, see Note C.
	Asset Retirement Obligations:   We record a liability for a legal ARO in the period in which it is incurred. When a new legal obligation is recorded, we capitalize the costs of the liability by increasing the carrying amount of the related long-lived asset. We accrete the liability to its present value each period and depreciate the capitalized cost over the useful life of the related asset. At the end of the asset's useful life, we settle the obligation for its recorded amount or incur a gain or loss. As it relates to our regulated operations, we apply regulatory accounting guidance and recognize regulatory assets or liabilities for the timing differences between when we recover legal AROs in rates and when we would recognize these costs. For further information, see Note E.
	Derivative Financial Instruments:   We have derivative physical and financial instruments which we report at fair value. For further information, see Note L.
	Cash and Cash Equivalents:   Cash and cash equivalents include marketable debt securities acquired three months or less from maturity.
	Margin Accounts:   Cash deposited in brokerage accounts for margin requirements is recorded in Other Current Assets on our Consolidated Balance Sheets.
	Restrictions:   Various financing arrangements and regulatory requirements impose certain restrictions on our ability to transfer funds to Wisconsin Energy in the form of cash dividends, loans or advances. In addition, under Wisconsin law, we are prohibited from loaning funds, either directly or indirectly, to Wisconsin Energy. We do not believe that these restrictions will materially affect our operations. For further information, see Note H.
	Impairment or Disposal of Long Lived Assets:   We carry property and equipment related to businesses held for sale at the lower of cost or estimated fair value less cost to sell. As of December 31, 2014, we had no assets classified as Held for Sale. Long-lived assets are tested for recoverability whenever events or changes in circumstances indicate that their carrying value may not be recoverable from the use and eventual disposition of the asset based on the remaining useful life. An impairment loss is recognized when the carrying amount of an asset is not recoverable and exceeds the fair value of the asset. The carrying amount of an asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. An impairment loss is measured as the excess of the carrying amount of the asset in comparison to the fair value of the asset.
	Investments:   We account for investments in other affiliated companies in which we do not maintain control using the equity method of accounting. We had a total ownership interest of approximately 23.0% in ATC as of December 31, 2014 and 2013. We are represented by one out of ten ATC board members, each of whom has one vote. Due to the voting requirements, no individual member has more than 10% of the voting control. For further information regarding such investments, see Note P.
	Income Taxes:   We follow the liability method in accounting for income taxes. Accounting guidance for income taxes requires the recording of deferred assets and liabilities to recognize the expected future tax consequences of events that have been reflected in our financial statements or tax returns and the adjustment of deferred tax balances to reflect tax rate changes. We are required to assess the likelihood that our deferred tax assets would expire before being realized.
	Investment tax credits related to regulated utility assets are recorded as a deferred credit on the balance sheet and amortized to income over the applicable service lives of related properties in accordance with regulatory treatment.
	We are included in Wisconsin Energy's consolidated Federal and state income tax returns. In accordance with our tax allocation agreement with Wisconsin Energy, we are allocated income tax payments and refunds based upon our separate tax computation. For further information on income taxes, see Note G.
	Wisconsin Energy allocates the tax benefit of exercised stock options to us to the extent the option holder's payroll cost was incurred by us. We record the allocated tax benefit as an addition to paid in capital.
	We recognize interest and penalties accrued related to unrecognized tax benefits in Income Taxes in our Consolidated Income Statements, as well as Regulatory Assets or Regulatory Liabilities in our Consolidated Balance Sheets.
	We collect sales and use taxes from our customers and remit these taxes to governmental authorities. These taxes are recorded in our Consolidated Income Statements on a net basis.
	Stock Options:   Our employees participate in the Wisconsin Energy stock-based compensation plan. The amounts reported represent the allocated costs related to options held by our employees.
	Wisconsin Energy estimates the fair value of stock options using the binomial pricing model. Historically, all stock options have been granted with an exercise price equal to the fair market value of the common stock on the date of grant and expire no later than 10 years from the grant date. Excess tax benefits are reported as a financing cash inflow. In addition, Wisconsin Energy reports unearned stock-based compensation associated with non-vested restricted stock and performance awards within other paid in capital in its Consolidated Statements of Common Equity. For a discussion of the impacts to our Consolidated Financial Statements, see Note H.
	The fair value of each Wisconsin Energy option was calculated using a binomial option pricing model using the following weighted-average assumptions:
		2014		2013	2012
	Risk-free interest rate	0.1% - 3.0%		0.1% - 1.9%	0.1% - 2.0%
	Dividend yield	3.80%		3.70%	3.90%
	Expected volatility	18.00%		18.00%	19.00%
	Expected life (years)	5.8		5.9	5.9
	Expected forfeiture rate	2.00%		2.00%	2.00%
	Weighted-average fair value
	of stock options granted	$4.18		$3.45	$3.34
	Treasury Grant:   In December 2013, we filed an application with the United States Treasury for a Section 1603 renewable energy grant related to the construction of our biomass facility in Rothschild, Wisconsin. The PSCW anticipated the recognition of this grant as income when it set rates for the two years beginning January 1, 2013. We provided bill credits to our customers in 2013 and 2014. For the years ended December 31, 2014 and 2013, $17.4 million and $48.0 million, respectively, was recognized as income, which reflects the amount that was returned to customers in the form of bill credits during the year. The accounting reflects the regulatory treatment of the grant.
	In June 2014, we received approximately $76.2 million related to the Treasury Grant. The PSCW approved escrow accounting for the Treasury Grant and the proceeds we received that exceeded the amounts originally included in rates are being returned to customers in the form of bill credits.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
SUPPLEMENTAL CASH FLOW INFORMATION	SUPPLEMENTAL CASH FLOW INFORMATION
	During the year ended December 31, 2014, we paid $117.9 million in interest, net of amounts capitalized, and paid $20.8 million in income taxes, net of refunds. During the year ended December 31, 2013, we paid $120.5 million in interest, net of amounts capitalized, and received $39.2 million in net refunds from income taxes. During the year ended December 31, 2012, we paid $109.0 million in interest, net of amounts capitalized, and received $91.2 million in net refunds from income taxes.
	As of December 31, 2014, 2013 and 2012, the amount of accounts payable related to capital expenditures was $1.7 million, $4.6 million and $15.7 million, respectively

Variable_Interest_Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2014
Variable Interest Entities [Abstract]
VARIABLE INTEREST ENTITIES	VARIABLE INTEREST ENTITIES
	The primary beneficiary of a variable interest entity must consolidate the related assets and liabilities. Certain disclosures are required by sponsors, significant interest holders in variable interest entities and potential variable interest entities.
	We assess our relationships with potential variable interest entities such as our coal suppliers, natural gas suppliers, coal and gas transporters, and other counterparties in power purchase agreements and joint ventures. In making this assessment, we consider the potential that our contracts or other arrangements provide subordinated financial support, the potential for us to absorb losses or rights to residual returns of the entity, the ability to directly or indirectly make decisions about the entities' activities and other factors.
	We have identified a purchased power agreement which represents a variable interest. This agreement is for 236 MW of firm capacity from a gas-fired cogeneration facility and we account for it as a capital lease. The agreement includes no minimum energy requirements over the remaining term of approximately eight years. We have examined the risks of the entity including operations and maintenance, dispatch, financing, fuel costs and other factors, and have determined that we are not the primary beneficiary of the entity. We do not hold an equity or debt interest in the entity and there is no residual guarantee associated with the purchased power agreement.
	We have approximately $174.0 million of required payments over the remaining term of this agreement. We believe that the required lease payments under this contract will continue to be recoverable in rates. Total capacity and lease payments under contracts considered variable interests in 2014, 2013 and 2012 were $53.0 million, $50.3 million and $45.8 million, respectively. Our maximum exposure to loss is limited to the capacity payments under the contract.

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]
	SCHEDULE II	VALUATION AND QUALIFYING ACCOUNTS
	Allowance for Doubtful Accounts		Balance at Beginning of the Period		Expense		Deferral		Net Write-offs			Balance at End of the Period
			(Millions of Dollars)
	December 31, 2014		$	39.7	$	31.3	$	10	$	(34.2	)	$	46.8
	December 31, 2013		$	36.7	$	31.4	$	2.7	$	(31.1	)	$	39.7
	December 31, 2012		$	36.9	$	8.7	$	20.7	$	(29.6	)	$	36.7

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies (Policies) [Abstract]
Consolidation	General:   Wisconsin Electric Power Company (Wisconsin Electric, the Company, our, us or we), a subsidiary of Wisconsin Energy, is an electric, gas and steam utility which services electric customers in Wisconsin and the Upper Peninsula of Michigan, gas customers in Wisconsin and steam customers in metropolitan Milwaukee, Wisconsin. We consolidate our wholly-owned subsidiary, Bostco. Bostco had total assets of $28.4 million and $29.1 million as of December 31, 2014 and 2013, respectively.
	All intercompany transactions and balances have been eliminated from the consolidated financial statements.
Basis of Accounting	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of certain assets and liabilities and disclosure of contingent assets and liabilities at the date of financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Revenues	Revenues:   We recognize energy revenues on the accrual basis and include estimated amounts for services rendered but not billed.
	Our retail electric rates in Wisconsin are established by the PSCW and include base amounts for fuel and purchased power costs. The electric fuel rules in Wisconsin allow us to defer, for subsequent rate recovery or refund, any under-collection or over-collection of fuel costs that are outside of the symmetrical fuel cost tolerance, which the PSCW set at plus or minus 2% of the approved fuel cost plan. The deferred under-collected amounts are subject to an excess revenues test.
	Our retail gas rates include monthly adjustments which permit the recovery or refund of actual purchased gas costs. We defer any difference between actual gas costs incurred (adjusted for a sharing mechanism) and costs recovered through rates as a current asset or liability. The deferred balance is returned to or recovered from customers at intervals throughout the year.
Accounting For MISO Energy Transactions	Accounting for MISO Energy Transactions:    The MISO Energy Markets operate under both day-ahead and real-time markets. We record energy transactions in the MISO Energy Markets on a net basis for each hour.
Property and Depreciation	Property and Depreciation:   We record property, plant and equipment at cost. Cost includes material, labor, overheads and capitalized interest. Utility property also includes AFUDC - Equity. Additions to and significant replacements of property are charged to property, plant and equipment at cost; minor items are charged to maintenance expense. The cost of depreciable utility property less salvage value is charged to accumulated depreciation when property is retired.
	Our utility depreciation rates are certified by the PSCW and MPSC and include estimates for salvage value and removal costs. Depreciation as a percent of average depreciable utility plant was 2.9% in 2014, 2013 and 2012.
	For assets other than our regulated assets and leased equipment, we accrue depreciation expense at straight-line rates over the estimated useful lives of the assets, or over the non-cancellable lease term for leased equipment.
	We collect in our rates amounts representing future removal costs for many assets that do not have an associated Asset Retirement Obligation (ARO). We record a regulatory liability on our balance sheet for the estimated amounts we have collected in rates for future removal costs less amounts we have spent in removal activities. This regulatory liability was $571.2 million as of December 31, 2014 and $558.9 million as of December 31, 2013.
Allowance for Funds Used During Construction, Policy [Policy Text Block]	Allowance For Funds Used During Construction:   AFUDC is included in utility plant accounts and represents the cost of borrowed funds (AFUDC - Debt) used during plant construction, and a return on stockholders' capital (AFUDC - Equity) used for construction purposes. AFUDC - Debt is recorded as a reduction of interest expense and AFUDC - Equity is recorded in Other Income and Deductions, net.
Materials, Supplies and Inventories	Materials, Supplies and Inventories:   Our inventory as of December 31 consists of:
	Materials, Supplies and Inventories	2014		2013
		(Millions of Dollars)
	Fossil Fuel	$	125.5	$	117.5
	Materials and Supplies	145		129.5
	Natural Gas in Storage	50		34
	Total	$	320.5	$	281
	Substantially all fossil fuel, materials and supplies and natural gas in storage inventories are recorded using the weighted-average cost method of accounting.
Regulatory Accounting	Regulatory Accounting:   The economic effects of regulation can result in regulated companies recording costs that have been or are expected to be allowed in the rate-making process in a period different from the period in which the costs would be charged to expense by an unregulated enterprise. When this occurs, costs are deferred as regulatory assets on the balance sheet and expensed in the periods when they are reflected in rates. We defer regulatory assets pursuant to specific or generic orders issued by our regulators. Additionally, regulators can impose regulatory liabilities upon a regulated company for amounts previously collected from customers and for amounts that are expected to be refunded to customers. In general, regulatory assets are recovered in a period between one to eight years. For further information, see Note C.
	A
Asset Retirement Obligations	Asset Retirement Obligations:   We record a liability for a legal ARO in the period in which it is incurred. When a new legal obligation is recorded, we capitalize the costs of the liability by increasing the carrying amount of the related long-lived asset. We accrete the liability to its present value each period and depreciate the capitalized cost over the useful life of the related asset. At the end of the asset's useful life, we settle the obligation for its recorded amount or incur a gain or loss. As it relates to our regulated operations, we apply regulatory accounting guidance and recognize regulatory assets or liabilities for the timing differences between when we recover legal AROs in rates and when we would recognize these costs. For further information, see Note E.
Derivative Financial Instruments	Derivative Financial Instruments:   We have derivative physical and financial instruments which we report at fair value. For further information, see Note L.
Cash and Cash Equivalents	Cash and Cash Equivalents:   Cash and cash equivalents include marketable debt securities acquired three months or less from maturity.
Margin Accounts	Margin Accounts:   Cash deposited in brokerage accounts for margin requirements is recorded in Other Current Assets on our Consolidated Balance Sheets.
Restrictions	Restrictions:   Various financing arrangements and regulatory requirements impose certain restrictions on our ability to transfer funds to Wisconsin Energy in the form of cash dividends, loans or advances. In addition, under Wisconsin law, we are prohibited from loaning funds, either directly or indirectly, to Wisconsin Energy. We do not believe that these restrictions will materially affect our operations. For further information, see Note H.
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	Impairment or Disposal of Long Lived Assets:   We carry property and equipment related to businesses held for sale at the lower of cost or estimated fair value less cost to sell. As of December 31, 2014, we had no assets classified as Held for Sale. Long-lived assets are tested for recoverability whenever events or changes in circumstances indicate that their carrying value may not be recoverable from the use and eventual disposition of the asset based on the remaining useful life. An impairment loss is recognized when the carrying amount of an asset is not recoverable and exceeds the fair value of the asset. The carrying amount of an asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. An impairment loss is measured as the excess of the carrying amount of the asset in comparison to the fair value of the asset.
Investments	Investments:   We account for investments in other affiliated companies in which we do not maintain control using the equity method of accounting. We had a total ownership interest of approximately 23.0% in ATC as of December 31, 2014 and 2013. We are represented by one out of ten ATC board members, each of whom has one vote. Due to the voting requirements, no individual member has more than 10% of the voting control. For further information regarding such investments, see Note P.
Income Taxes	Income Taxes:   We follow the liability method in accounting for income taxes. Accounting guidance for income taxes requires the recording of deferred assets and liabilities to recognize the expected future tax consequences of events that have been reflected in our financial statements or tax returns and the adjustment of deferred tax balances to reflect tax rate changes. We are required to assess the likelihood that our deferred tax assets would expire before being realized.
	Investment tax credits related to regulated utility assets are recorded as a deferred credit on the balance sheet and amortized to income over the applicable service lives of related properties in accordance with regulatory treatment.
	We are included in Wisconsin Energy's consolidated Federal and state income tax returns. In accordance with our tax allocation agreement with Wisconsin Energy, we are allocated income tax payments and refunds based upon our separate tax computation. For further information on income taxes, see Note G.
	Wisconsin Energy allocates the tax benefit of exercised stock options to us to the extent the option holder's payroll cost was incurred by us. We record the allocated tax benefit as an addition to paid in capital.
	We recognize interest and penalties accrued related to unrecognized tax benefits in Income Taxes in our Consolidated Income Statements, as well as Regulatory Assets or Regulatory Liabilities in our Consolidated Balance Sheets.
	We collect sales and use taxes from our customers and remit these taxes to governmental authorities. These taxes are recorded in our Consolidated Income Statements on a net basis.
Stock Options	Stock Options:   Our employees participate in the Wisconsin Energy stock-based compensation plan. The amounts reported represent the allocated costs related to options held by our employees.
	Wisconsin Energy estimates the fair value of stock options using the binomial pricing model. Historically, all stock options have been granted with an exercise price equal to the fair market value of the common stock on the date of grant and expire no later than 10 years from the grant date. Excess tax benefits are reported as a financing cash inflow. In addition, Wisconsin Energy reports unearned stock-based compensation associated with non-vested restricted stock and performance awards within other paid in capital in its Consolidated Statements of Common Equity. For a discussion of the impacts to our Consolidated Financial Statements, see Note H.
Treasury Grant Accounting Policy [Policy Text Block]	Treasury Grant:   In December 2013, we filed an application with the United States Treasury for a Section 1603 renewable energy grant related to the construction of our biomass facility in Rothschild, Wisconsin. The PSCW anticipated the recognition of this grant as income when it set rates for the two years beginning January 1, 2013. We provided bill credits to our customers in 2013 and 2014. For the years ended December 31, 2014 and 2013, $17.4 million and $48.0 million, respectively, was recognized as income, which reflects the amount that was returned to customers in the form of bill credits during the year. The accounting reflects the regulatory treatment of the grant.
	In June 2014, we received approximately $76.2 million related to the Treasury Grant. The PSCW approved escrow accounting for the Treasury Grant and the proceeds we received that exceeded the amounts originally included in rates are being returned to customers in the form of bill credits.

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligations (Tables) [Abstract]
Change in Asset Retirement Obligations	The following table presents the change in our AROs during 2014 and 2013:
		2014			2013
		(Millions of Dollars)
	Balance as of January 1	$	39.4		$	41.5
	Liabilities Settled	(1.1		)	(4.3		)
	Accretion	2.2			2.2
	Balance as of December 31	$	40.5		$	39.4

Benefits_Tables

Benefits (Tables)	12 Months Ended
	Dec. 31, 2014
Benefits (Tables) [Abstract]
Details about pension and OPEB plans	The following table presents details about the pension and OPEB plans:
			Pension						OPEB
			2014			2013			2014			2013
			(Millions of Dollars)
	Change in Benefit Obligation
	Benefit Obligation at January 1		$	1,223.10		$	1,310.30		$	292.4		$	305.4
	Service cost		9.4			13.9			8.1			9.5
	Interest cost		59.3			52.4			14.4			12.7
	Participants' contributions		—			—			8.4			8.1
	Plan amendments		—			(0.9		)	(5.2		)	—
	Actuarial loss (gain)		110.8			(73.9		)	24.3			(22.7		)
	Other accrued benefits		(0.1		)	—			—			—
	Gross benefits paid		(87.3		)	(78.7		)	(21.1		)	(21.3		)
	Federal subsidy on benefits paid		N/A			N/A			1			0.7
	Benefit Obligation at December 31		$	1,315.20		$	1,223.10		$	322.3		$	292.4
	Change in Plan Assets
	Fair Value at January 1		$	1,168.90		$	1,121.10		$	222.4		$	194.8
	Actual earnings on plan assets		71.2			119			12			30.7
	Employer contributions		7.2			7.5			3.2			10.1
	Participants' contributions		—			—			8.4			8.1
	Gross benefits paid		(87.3		)	(78.7		)	(21.1		)	(21.3		)
	Fair Value at December 31		$	1,160.00		$	1,168.90		$	224.9		$	222.4
	Net liability		$	155.2		$	54.2		$	97.4		$	70
Amounts recognized in Consolidated Balance Sheets	Amounts recognized in our Consolidated Balance Sheets as of December 31 related to the funded status of the benefit plans consisted of:
			Pension						OPEB
			2014			2013			2014			2013
			(Millions of Dollars)
	Other long-term assets		$	—		$	34.3		$	1.9		$	1.6
	Other long-term liabilities		$	155.2		$	88.5		$	99.3		$	71.6
	Net liability		$	155.2		$	54.2		$	97.4		$	70
Amounts not yet been recognized in net periodic benefit cost	The following table shows the amounts that have not yet been recognized in our net periodic benefit cost as of December 31 and are recorded as a regulatory asset on our balance sheet:
			Pension						OPEB
			2014			2013			2014			2013
			(Millions of Dollars)
	Net actuarial loss (gain)		$	476.4		$	384.7		$	20.7		$	(7.6	)
	Prior service costs (credits)		6.3			8.3			(5.2		)	(1.7		)
	Total - Regulatory Assets (Liabilities)		$	482.7		$	393		$	15.5		$	(9.3	)
Components of net periodic pension and OPEB costs	The components of net periodic pension and OPEB costs for the years ended December 31 are as follows:
			Pension									OPEB
			2014			2013			2012			2014			2013			2012
			(Millions of Dollars)
	Net Periodic Benefit Cost
	Service cost		$	9.4		$	13.9		$	19.8		$	8.1		$	9.5		$	9.8
	Interest cost		59.3			52.4			56.8			14.4			12.7			16.7
	Expected return on plan assets		(79.1		)	(77.2		)	(71.8		)	(16.2		)	(14.5		)	(13.0		)
	Amortization of:
	Transition obligation		—			—			—			—			—			0.3
	Prior service cost (credit)		2			2.2			2.1			(1.7		)	(1.9		)	(1.9		)
	Actuarial loss		26.9			41.7			30.6			0.2			1.5			5
	Settlement charge		—			1.5			—			—			—			—
	Other		—			—			0.4			—			—			—
	Net Periodic Benefit Cost		$	18.5		$	34.5		$	37.9		$	4.8		$	7.3		$	16.9
			Pension					OPEB
			2014		2013	2012		2014	2013		2012
	Weighted-Average assumptions used to
	determine benefit obligations as of Dec. 31
	Discount rate		4.15%		5.00%	4.10%		4.20%	4.95%		4.15%
	Rate of compensation increase		4.00%		4.00%	4.00%		N/A	N/A		N/A
	Weighted-Average assumptions used to
	determine net cost for year ended Dec. 31
	Discount rate		5.00%		4.10%	5.05%		4.95%	4.15%		5.20%
	Expected return on plan assets		7.25%		7.25%	7.25%		7.50%	7.50%		7.50%
	Rate of compensation increase		4.00%		4.00%	4.00%		N/A	N/A		N/A
	Assumed health care cost trend rates as of Dec. 31
	Health care cost trend rate assumed for next year (Pre 65 / Post 65)							7.5%/7.5%	7.5%/7.5%		7.5%/7.5%
	Rate that the cost trend rate gradually adjusts to							5.00%	5.00%		5.00%
	Year that the rate reaches the rate it is assumed to remain at (Pre 65 / Post 65)							2021/2021	2021/2021		2017/2017
A one-percentage-point change in assumed health care cost trend rates effects	A one-percentage-point change in assumed health care cost trend rates would have the following effects:
			1% Increase			1% Decrease
			(Millions of Dollars)
	Effect on
	Post-retirement benefit obligation		$	29.3		$	(24.4	)
	Total of service and interest cost components		$	3.1		$	(2.5	)
Summary of fair value of plan assets by asset category within fair value hierarchy	The following table summarizes the fair value of our share of plan assets by asset category within the fair value hierarchy (for further level information, see Note M):
			As of December 31, 2014
	Asset Category - Pension		Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Cash and Cash Equivalents		$	5.1		$	—		$	—		$	5.1
	Equities:
	U.S. Equity		404.5			—			—			404.5
	International Equity		103.3			23.9			—			127.2
	Fixed Income:
	Short, Intermediate and Long-term Bonds (a)
	U.S. Bonds		34.2			481.2			—			515.4
	International Bonds		63.7			34.8			—			98.5
	Private equity and real estate		—			—			9.3			9.3
	Total		$	610.8		$	539.9		$	9.3		$	1,160.00
			As of December 31, 2013
	Asset Category - Pension		Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Cash and Cash Equivalents		$	16.9		$	—		$	—		$	16.9
	Equities:
	U.S. Equity		418.5			—			—			418.5
	International Equity		117.8			28.8			—			146.6
	Fixed Income:
	Short, Intermediate and Long-term Bonds (a)
	U.S. Bonds		87.3			407			—			494.3
	International Bonds		62.9			29.7			—			92.6
	Total		$	703.4		$	465.5		$	—		$	1,168.90
	(a)	This category represents investment grade bonds of U.S. and foreign issuers denominated in U.S. dollars from diverse industries.
	The following table summarizes the fair value of our share of OPEB plan assets by asset category within the fair value hierarchy:
			As of December 31, 2014
	Asset Category - OPEB		Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Cash and Cash Equivalents		$	0.9		$	—		$	—		$	0.9
	Equities:
	U.S. Equity		98.4			—			—			98.4
	International Equity		28.5			1.7			—			30.2
	Fixed Income:
	Short, Intermediate and Long-term Bonds (a)
	U.S. Bonds		2.4			75.8			—			78.2
	International Bonds		11.8			4.7			—			16.5
	Private equity and real estate		—			—			0.7			0.7
	Total		$	142		$	82.2		$	0.7		$	224.9
			As of December 31, 2013
	Asset Category - OPEB		Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Cash and Cash Equivalents		$	1.8		$	—		$	—		$	1.8
	Equities:
	U.S. Equity		100.5			—			—			100.5
	International Equity		31.8			1.9			—			33.7
	Fixed Income:
	Short, Intermediate and Long-term Bonds (a)
	U.S. Bonds		5.7			65.4			—			71.1
	International Bonds		11.4			3.9			—			15.3
	Total		$	151.2		$	71.2		$	—		$	222.4
	(a)	This category represents investment grade bonds of U.S. and foreign issuers denominated in U.S. dollars from diverse industries.
Employer contributions to defined benefit plan	Cash Flows:
	Historical employer contributions:
			Pension
	Year		Qualified			Non-Qualified			OPEB
			(Millions of Dollars)
	2012		$	88.5		$	6		$	13.6
	2013		$	—		$	7.5		$	10.1
	2014		$	—		$	7.2		$	3.2
Expected benefit payments in future
	Year		Pension			Gross OPEB
			(Millions of Dollars)
	2015		$	91.8		$	13.9
	2016		$	91.5		$	14.8
	2017		$	92.1		$	16
	2018		$	89.5		$	17.1
	2019		$	89.4		$	18.2
	2020-2024		$	429.5		$	99.3

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies (Tables) [Abstract]
Future minimum payments for the next five years and thereafter for our operating lease contracts	Future minimum payments for the next five years and thereafter for our operating lease contracts are as follows:
		(Millions of Dollars)
	2015	$	5.2
	2016	3.9
	2017	3.2
	2018	3.1
	2019	1.2
	Thereafter	21.5
	Total	$	38.1

Derivative_Instruments_Tables

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments (Tables) [Abstract]
Derivative instruments in balance sheet	We record our current derivative assets on the balance sheet in other current assets and the current portion of the liabilities in other current liabilities. The long-term portion of our derivative assets of $0.6 million is recorded in other deferred charges and other assets as of December 31, 2014, and the long-term portion of derivative liabilities of $0.7 million is recorded in other deferred credit and other liabilities as of December 31, 2014. Our Consolidated Balance Sheets as of December 31, 2014 and 2013 include:
			December 31, 2014								December 31, 2013
			Derivative				Derivative				Derivative				Derivative
			Asset				Liability				Asset				Liability
			(Millions of Dollars)
	Natural Gas		$	2.3			$	7.1			$	2.8			$	0.1
	Fuel Oil		—				—				0.6				—
	FTRs		7				—				3.5				—
	Coal		3.3				0.2				2.1				0.2
	Total		$	12.6			$	7.3			$	9			$	0.3
Derivative instruments' estimated notional volumes and gain (losses)	Our Consolidated Income Statements include gains (losses) on derivative instruments used in our risk management strategies under fuel and purchased power for those commodities supporting our electric operations and under cost of gas sold for the natural gas sold to our customers. Our estimated notional volumes and gains (losses) for the years ended December 31, 2014 and 2013 were as follows:
			2014						2013
			Volume		Gains				Volume		Gains (Losses)
					(Millions of Dollars)						(Millions of Dollars)
	Natural Gas		21.4 million Dth		$	4			24.0 million Dth		$	(4.0	)
	Fuel Oil		9.2 million gallons		0.5				8.6 million gallons		0.5
	FTRs		26.1 million MWh		12.7				25.3 million MWh		14.9
	Total				$	17.2					$	11.4
Offsetting Assets and Liabilities [Table Text Block]
		December 31, 2014								December 31, 2013
		Derivative				Derivative				Derivative				Derivative
		Asset				Liability				Asset				Liability
		(Millions of Dollars)
	Gross Amount Recognized on the Balance Sheet	$	12.6			$	7.3			$	9			$	0.3
	Gross Amount Not Offset on Balance Sheet (a)	(0.4		)		(6.8		)		—				—
	Net Amount	$	12.2			$	0.5			$	9			$	0.3
	(a)	Gross Amount Not Offset on Balance Sheet includes cash collateral posted of $6.4 million and zero as of December 31, 2014 and 2013, respectively.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements (Tables) [Abstract]
Financial assets and liabilities by level within the fair value hierarchy	The following tables summarize our financial assets and liabilities by level within the fair value hierarchy:
	Recurring Fair Value Measures	As of December 31, 2014
		Level 1			Level 2			Level 3		Total
		(Millions of Dollars)
	Assets:
	Derivatives	$	0.4		$	5.2		$	7	$	12.6
	Total	$	0.4		$	5.2		$	7	$	12.6
	Liabilities:
	Derivatives	$	6.8		$	0.5		$	—	$	7.3
	Total	$	6.8		$	0.5		$	—	$	7.3
	Recurring Fair Value Measures	As of December 31, 2013
		Level 1			Level 2			Level 3		Total
		(Millions of Dollars)
	Assets:
	Derivatives	$	3.2		$	2.3		$	3.5	$	9
	Total	$	3.2		$	2.3		$	3.5	$	9
	Liabilities:
	Derivatives	$	—		$	0.3		$	—	$	0.3
	Total	$	—		$	0.3		$	—	$	0.3
Fair value of derivatives classified as Level 3 in the fair value hierarchy	The following table summarizes the changes to derivatives classified as Level 3 in the fair value hierarchy:
		2014			2013
		(Millions of Dollars)
	Balance as of January 1	$	3.5		$	4.7
	Realized and unrealized gains (losses)	—			—
	Purchases	15.6			10.6
	Issuances	—			—
	Settlements	(12.1		)	(11.8		)
	Transfers in and/or out of Level 3	—			—
	Balance as of December 31	$	7		$	3.5
Carrying amount and estimated fair value of certain financial instruments	The carrying amount and estimated fair value of certain of our recorded financial instruments as of December 31 are as follows:
		2014						2013
		Carrying			Fair			Carrying		Fair
	Financial Instruments	Amount			Value			Amount		Value
		(Millions of Dollars)
	Preferred stock, no redemption required	$	30.4		$	27.1		$	30.4	$	26
	Long-term debt including current portion	$	2,437.00		$	2,759.60		$	2,487.00	$	2,634.70

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes (Tables) [Abstract]
Summary of income tax expense	The following table is a summary of income tax expense for each of the years ended December 31:
	Income Taxes		2014				2013				2012
			(Millions of Dollars)
	Current tax expense (benefit)		$	31.2			$	7.3			$	(1.4	)
	Deferred income taxes, net		192.5				194.7				195.2
	Investment tax credit, net		(1.1		)		(1.1		)		(1.1		)
	Total Income Tax Expense		$	222.6			$	200.9			$	192.7
The provision for income taxes for each of the years ended December 31 differs from the amount of income tax determined by applying the applicable U.S. statutory federal income tax rate to income before income taxes as a result of the following:	The provision for income taxes for each of the years ended December 31 differs from the amount of income tax determined by applying the applicable U.S. statutory federal income tax rate to income before income taxes and preferred dividend as a result of the following:
			2014							2013						2012
							Effective							Effective					Effective
	Income Tax Expense		Amount				Tax Rate			Amount				Tax Rate		Amount			Tax Rate
			(Millions of Dollars)
	Expected tax at statutory federal tax rates		$	209.8			35	%		$	196.3			35	%	$	195.6		35	%
	State income taxes net of federal tax benefit		33				5.5	%		31.7				5.6	%	28.8			5.1	%
	Production tax credits		(17.4		)		(2.9	)%		(16.7		)		(3.0	)%	(15.9		)	(2.8	)%
	Treasury Grant		(3.8		)		(0.6	)%		(7.4		)		(1.3	)%	—			—	%
	AFUDC - Equity		(1.5		)		(0.2	)%		(6.1		)		(1.1	)%	(12.2		)	(2.2	)%
	Investment tax credit restored		(1.1		)		(0.2	)%		(1.1		)		(0.2	)%	(1.1		)	(0.2	)%
	Domestic production activities deduction		—				—	%		—				—	%	(12.6		)	(2.3	)%
	Other, net		3.6				0.5	%		4.2				0.7	%	10.1			1.8	%
	Total Income Tax Expense		$	222.6			37.1	%		$	200.9			35.7	%	$	192.7		34.4	%
Components of deferred income taxes classified as net current assets and net long-term liabilities	The components of deferred income taxes classified as net current assets and net long-term liabilities as of December 31 are as follows:
	Deferred Tax Assets		2014				2013
			(Millions of Dollars)
	Current
	Future federal tax benefits		$	56			$	113.1
	Uncollectible account expense		15.6				17.2
	Employee benefits and compensation		11.6				11.7
	Recoverable gas costs		1				0.5
	Other		2.3				3.3
	Total Current Deferred Tax Assets		86.5				145.8
	Non-current
	Deferred revenues		221.3				237
	Employee benefits and compensation		92.1				92.4
	Construction advances		15.5				15
	Emission Allowances		0.1				—
	Other		31.7				42.2
	Total Non-Current Deferred Tax Assets		360.7				386.6
	Total Deferred Tax Assets		$	447.2			$	532.4
	Deferred Tax Liabilities		2014				2013
			(Millions of Dollars)
	Current
	Prepaid items		$	39.8			$	70
	Total Current Deferred Tax Liabilities		39.8				70
	Non-current
	Property-related		1,942.20				1,820.90
	Investment in transmission affiliate		164.1				147.8
	Employee benefits and compensation		131.2				135
	Deferred transmission costs		58.5				50.8
	Other		28.6				26.6
	Total Non-current Deferred Tax Liabilities		2,324.60				2,181.10
	Total Deferred Tax Liabilities		$	2,364.40			$	2,251.10
	Consolidated Balance Sheet Presentation		2014				2013
	Current Deferred Tax Asset		$	46.7			$	75.8
	Non-Current Deferred Tax Liability		$	1,963.90			$	1,794.50
Reconciliation of the beginning and ending amount of unrecognized tax benefits	e previously adopted accounting guidance related to uncertainty in income taxes. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:
		2014				2013
		(Millions of Dollars)
	Balance as of January 1	$	8.4			$	10.8
	Reductions for tax positions of prior years	(1.2		)		(2.4		)
	Balance as of December 31	$	7.2			$	8.4

LongTerm_Debt_and_Capital_Leas1

Long-Term Debt and Capital Lease Obligations (Tables)	12 Months Ended
	Dec. 31, 2014
Long-Term Debt and Capital Lease Obligations (Tables) [Abstract]
Long-term debt outstanding maturities and sinking fund requirements	Debentures and Notes:   As of December 31, 2014, the maturities of our long-term debt outstanding (excluding obligations under capital leases) were as follows:
		(Millions of Dollars)
	2015	$	250
	2016	—
	2017	—
	2018	250
	2019	250
	Thereafter	1,687.00
	Total	$	2,437.00
Captial Lease Payments [Table Text Block]	We paid the following lease payments during 2014, 2013 and 2012:
			2014			2013			2012
			(Millions of Dollars)
	Long-term power purchase commitment		$	34.9		$	33.7		$	32.5
	PWGS		99.2			99.1			99
	Oak Creek Expansion		277.8			274.9			269.3
	Total		$	411.9		$	407.7		$	400.8
Summary of capitalized leased facilities	The following table summarizes our capitalized leased facilities as of December 31:
	Capital Lease Assets		2014			2013
			(Millions of Dollars)
	Long-term Power Purchase Commitment
	Under capital lease		$	140.3		$	140.3
	Accumulated amortization		(98.3		)	(92.5		)
	Total Long-term Power Purchase Commitment		$	42		$	47.8
	PWGS
	Under capital lease		$	682.7		$	681.5
	Accumulated amortization		(217.6		)	(190.1		)
	Total PWGS		$	465.1		$	491.4
	Oak Creek Expansion
	Under capital lease		$	2,025.60		$	1,991.10
	Accumulated amortization		(317.7		)	(251.3		)
	Total Oak Creek		$	1,707.90		$	1,739.80
	Total Leased Facilities		$	2,215.00		$	2,279.00
Future minimum lease payments under capital lease and present value of net minimum lease payments	Future minimum lease payments under our capital leases and the present value of our net minimum lease payments as of December 31, 2014 are as follows:
			Power
			Purchase						Oak Creek
	Capital Lease Obligations		Commitment			PWGS			Expansion			Total
			(Millions of Dollars)
	2015		$	43.5		$	99.3		$	296.4		$	439.2
	2016		45.1			99.3			311			455.4
	2017		13.9			99.3			311.4			424.6
	2018		14.7			99.3			311.4			425.4
	2019		15.5			99.3			311.4			426.2
	Thereafter		41.3			1,184.70			6,378.50			7,604.50
	Total Minimum Lease Payments		174			1,681.20			7,920.10			9,775.30
	Less:  Estimated Executory Costs		(54.7		)	—			—			(54.7		)
	Net Minimum Lease Payments		119.3			1,681.20			7,920.10			9,720.60
	Less:  Interest		(34.8		)	(1,044.1		)	(5,823.6		)	(6,902.5		)
	Present Value of Net
	Minimum Lease Payments		84.5			637.1			2,096.50			2,818.10
	Less:  Due Currently		(24.6		)	(10.2		)	(70.8		)	(105.6		)
	Total Capital Lease Obligations		$	59.9		$	626.9		$	2,025.70		$	2,712.50

Regulatory_Assets_and_Liabilit1

Regulatory Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Regulatory Assets and Liabilities (Tables) [Abstract]
Regulatory assets and liabilities	Our regulatory assets and liabilities as of December 31 consist of:
		2014		2013
		(Millions of Dollars)
	Regulatory Assets
	Deferred plant related -- capital leases	$	603	$	512.5
	Deferred unrecognized pension costs	482.8		393
	Deferred income tax related	171.5		165.8
	Escrowed electric transmission costs	146		126.8
	Other, net	223.6		172.2
	Total regulatory assets	$	1,626.90	$	1,370.30
	Regulatory Liabilities
	Deferred cost of removal obligations	$	571.2	$	558.9
	Other, net	44.7		75.3
	Total regulatory liabilities	$	615.9	$	634.2

Related_Parties_Tables

Related Parties (Tables)	12 Months Ended
	Dec. 31, 2014
Related Party Transaction [Line Items]
Related Party Transactions Disclosure [Text Block]	During the years ended December 31, 2014, 2013 and 2012, our equity in earnings and distributions received from ATC were as follows:
	Equity Investee	2014		2013		2012
		(Millions of Dollars)
	Equity in Earnings	$	57.9	$	60.2	$	57.6
	Distributions Received	$	50.5	$	47.8	$	46.1
ATC financial information [Table Text Block]	Summary financial information as of December 31 from the financial statements of ATC is as follows:
		2014		2013		2012
		(Millions of Dollars)
	Operating Revenues	$	635	$	626.3	$	603.3
	Operating Income	$	327.6	$	331.3	$	322.2
	Net Income	$	238.7	$	247.6	$	237.4
	Current Assets	$	66.4	$	80.7	$	63.1
	Non-Current Assets	$	3,728.70	$	3,509.50	$	3,274.70
	Current Liabilities	$	313.1	$	381.5	$	251.5
	Non-Current Liabilities	$	1,864.80	$	1,676.20	$	1,645.80
Provided and received services from the associated companies	We provided and received services from the following associated companies during 2014, 2013 and 2012:
	Company	2014		2013		2012
		(Millions of Dollars)
	Affiliate
	Services Provided
	We Power (excluding lease payments)	$	41.5	$	2.8	$	2.3
	Wisconsin Gas	$	81.7	$	83.4	$	78.7
	Wisconsin Energy	$	11.3	$	5.6	$	5.6
	Other	$	1.5	$	1.6	$	1.2
	Services Received
	We Power (including lease payments)	$	389	$	381.7	$	375.3
	Wisconsin Gas	$	20.6	$	23.6	$	16.6
	Wisconsin Energy	$	15.2	$	10.2	$	23.9
	Equity Investee - ATC
	Services Provided	$	8.1	$	9	$	8.2
	Services Received	$	231.4	$	234.2	$	222.7
Receivable and payable balances with ATC	As of December 31, 2014 and 2013, our Consolidated Balance Sheets included receivable and payable balances with ATC as follows:
	Equity Investee	2014		2013
		(Millions of Dollars)
	Accounts Receivable
	Services provided	$	0.6	$	0.6
	Accounts Payable
	Services received	$	19.3	$	19.5

Segment_Reporting_Tables

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting (Tables) [Abstract]
Financial information of reportable operating segments	Summarized financial information concerning our reportable segments for each of the three years ended December 31, 2014 is shown in the following table:
			Reportable Segments
	Year Ended		Electric		Gas		Steam			Other (a)		Total
			(Millions of Dollars)
	December 31, 2014
	Operating Revenues (b)		$	3,401.10	$	614.2	$	44.1		$	—	$	4,059.40
	Depreciation and Amortization		$	261.5	$	30.5	$	3.7		$	—	$	295.7
	Operating Income (c)		$	565.6	$	77.2	$	7.6		$	—	$	650.4
	Equity in Earnings
	of Transmission Affiliate		$	57.9	$	—	$	—		$	—	$	57.9
	Capital Expenditures		$	470.2	$	67.9	$	2.8		$	—	$	540.9
	December 31, 2013
	Operating Revenues (b)		$	3,308.70	$	451.9	$	39.6		$	—	$	3,800.20
	Depreciation and Amortization		$	249.5	$	25.5	$	3.6		$	—	$	278.6
	Operating Income (Loss) (c)		$	533.2	$	69.8	$	2.9		$	—	$	605.9
	Equity in Earnings
	of Transmission Affiliate		$	60.2	$	—	$	—		$	—	$	60.2
	Capital Expenditures		$	438.5	$	57.8	$	10.6		$	—	$	506.9
	December 31, 2012
	Operating Revenues (b)		$	3,193.90	$	385.1	$	34.3		$	—	$	3,613.30
	Depreciation and Amortization		$	230.3	$	23.9	$	3.4		$	—	$	257.6
	Operating Income (c)		$	536.5	$	50	$	(3.2	)	$	—	$	583.3
	Equity in Earnings
	of Transmission Affiliate		$	57.6	$	—	$	—		$	—	$	57.6
	Capital Expenditures		$	524.9	$	50.8	$	—		$	0.1	$	575.8
	(a)	Other includes primarily non-utility property and investments, materials and supplies, deferred charges and other corporate items.
	(b)	We account for intersegment revenues at a tariff rate established by the PSCW. Intersegment revenues were not material.
	(c)	We evaluate operating income to manage our utility business. Equity in Earnings of Transmission Affiliate, Interest Expense and Income Taxes are not included in segment operating income.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies (Tables) [Abstract]
Other Income and Deductions, Net	Other Income and Deductions, Net:   We recorded the following items in Other Income and Deductions, net for the years ended December 31:
	Other Income and Deductions, net		2014			2013			2012
			(Millions of Dollars)
	AFUDC - Equity		$	4.4		$	17.6		$	34.9
	Gain on Property Sales		4.3			0.8			0.3
	Other, net		—			(1.0		)	(2.9		)
	Total Other Income and Deductions, net		$	8.7		$	17.4		$	32.3
Property In Service By Segment	Property and Depreciation:   We record property, plant and equipment at cost. Cost includes material, labor, overheads and capitalized interest. Utility property also includes AFUDC - Equity. Additions to and significant replacements of property are charged to property, plant and equipment at cost; minor items are charged to maintenance expense. The cost of depreciable utility property less salvage value is charged to accumulated depreciation when property is retired.
	Our utility depreciation rates are certified by the PSCW and MPSC and include estimates for salvage value and removal costs. Depreciation as a percent of average depreciable utility plant was 2.9% in 2014, 2013 and 2012.
	For assets other than our regulated assets and leased equipment, we accrue depreciation expense at straight-line rates over the estimated useful lives of the assets, or over the non-cancellable lease term for leased equipment.
	We collect in our rates amounts representing future removal costs for many assets that do not have an associated Asset Retirement Obligation (ARO). We record a regulatory liability on our balance sheet for the estimated amounts we have collected in rates for future removal costs less amounts we have spent in removal activities. This regulatory liability was $571.2 million as of December 31, 2014 and $558.9 million as of December 31, 2013.
Allowance For Funds Used During Construction	We recorded the following AFUDC for the years ended December 31:
			2014			2013			2012
			(Millions of Dollars)
	AFUDC - Debt		$	1.8		$	7.4		$	14.5
	AFUDC - Equity		$	4.4		$	17.6		$	34.9
Fair value of stock options	The fair value of each Wisconsin Energy option was calculated using a binomial option pricing model using the following weighted-average assumptions:
		2014		2013	2012
	Risk-free interest rate	0.1% - 3.0%		0.1% - 1.9%	0.1% - 2.0%
	Dividend yield	3.80%		3.70%	3.90%
	Expected volatility	18.00%		18.00%	19.00%
	Expected life (years)	5.8		5.9	5.9
	Expected forfeiture rate	2.00%		2.00%	2.00%
	Weighted-average fair value
	of stock options granted	$4.18		$3.45	$3.34
Inventory Disclosure [Text Block]	Materials, Supplies and Inventories:   Our inventory as of December 31 consists of:
	Materials, Supplies and Inventories		2014			2013
			(Millions of Dollars)
	Fossil Fuel		$	125.5		$	117.5
	Materials and Supplies		145			129.5
	Natural Gas in Storage		50			34
	Total		$	320.5		$	281
	Substantially all fossil fuel, materials and supplies and natural gas in storage inventories are recorded using the weighted-average cost method of accounting.

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental Cash Flow Information (Textuals)
Interest paid, net of amounts capitalized	$117.90	$120.50	$109
Net refunds from income taxes		39.2	91.2
Income taxes paid, net of refunds	20.8
Accounts payable related to capital expenditures	1.7	4.6	15.7
Treasury Grant	$17.40	$48	$0

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Megawatt
Variable Interest Entities (Textuals)
Power capacity from a gas-fired cogeneration facility under capital lease (MW)	236
Capital Lease Agreements With VIE Remaining Term In Years	8 years
Total payments over remaining terms of the two agreements	$174
Total capacity and minimum lease payments	$53	$50.30	$45.80

Acquisition_Details

Acquisition (Details) (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014
Acquisition [Abstract]
Business Acquisition, Date of Acquisition Agreement	22-Jun-14
Number of WEC shares per Integrys share	1.128
Cash per share of Integrys common stock	$18.58
Estimate of number of WEC shares to be issued for acquisition	91,000,000
Estimate of acquisition-related debt	$1.50

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Change in Asset Retirement Obligations
Balance as of January 1	$39.40	$41.50
Liabilities settled	-1.1	-4.3
Accretion	2.2	2.2
Balance as of December 31	$40.50	$39.40

Benefits_Details

Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
New 401k Contribution for new hires				6.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$1,160,000,000	$1,168,900,000	$1,121,100,000
Change in Benefit Obligation
Benefit Obligation at January 1	1,223,100,000	1,310,300,000
Service cost	9,400,000	13,900,000	19,800,000
Interest cost	59,300,000	52,400,000	56,800,000
Participants' contributions	0	0
Plan amendments	0	-900,000
Actuarial loss (gain)	110,800,000	-73,900,000
Defined Benefit Plan, Special Termination Benefits	-100,000	0
Gross benefits paid	-87,300,000	-78,700,000
Benefit Obligation at December 31	1,315,200,000	1,223,100,000	1,310,300,000
Defined Benefit Plan, Actual Return on Plan Assets	71,200,000	119,000,000
Defined Benefit Plan, Contributions by Employer	7,200,000	7,500,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities	155,200,000	54,200,000
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	224,900,000	222,400,000	194,800,000
Change in Benefit Obligation
Benefit Obligation at January 1	292,400,000	305,400,000
Service cost	8,100,000	9,500,000	9,800,000
Interest cost	14,400,000	12,700,000	16,700,000
Participants' contributions	8,400,000	8,100,000
Plan amendments	-5,200,000	0
Actuarial loss (gain)	24,300,000	-22,700,000
Defined Benefit Plan, Special Termination Benefits	0	0
Gross benefits paid	-21,100,000	-21,300,000
Federal subsidy on benefits paid	1,000,000	700,000
Benefit Obligation at December 31	322,300,000	292,400,000	305,400,000
Defined Benefit Plan, Actual Return on Plan Assets	12,000,000	30,700,000
Defined Benefit Plan, Contributions by Employer	3,200,000	10,100,000	13,600,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities	$97,400,000	$70,000,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Future minimum payments for the next five years and thereafter for our operating lease contracts
2014	$5.20
2015	3.9
2016	3.2
2017	3.1
2018	1.2
Thereafter	21.5
Total	38.1
Manufactured Gas Plant Sites [Member]
Commitments and Contingencies (Textuals) [Abstract]
Estimated future detailed site investigation and remediation costs, minimum	6
Estimated Future detailed site investigation and remediation costs, maximum	12
Period for future costs of detailed site investigation and remediation costs	over the next ten years
Reserves related to future remediation costs	6.5	10.8
Period to recover remediation cost of manufactured gas plant sites	5 years
Coal combustion product landfill sites [Member]
Commitment and Contingencies (Textuals) [Abstract]
Expense related to environmental remediation	0.1	0.1	0.3
Reserves related to landfill sites	0
Commitments and Contingencies (Textuals) [Abstract]
Expense related to environmental remediation	$0.10	$0.10	$0.30

Common_Equity_Details

Common Equity (Details) (USD $)	12 Months Ended				1 Months Ended				3 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Mar. 31, 2014
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense	$18.40	$17.30	$18.80
Related Tax Benefit	7.4	6.9	7.5
Common Equity (Textuals)
Actual tax benefit realized for the tax deductions from option exercises/settlement	18.8	16.6	0
Common Stock, shares, outstanding	33,289,327	33,289,327
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$30.07
Maximum [Member]
Common Equity (Textuals)
Requirement to maintain common equity ratio by Wisconsin Electric				53.50%
Minimum [Member]
Common Equity (Textuals)
Requirement to maintain common equity ratio by Wisconsin Electric				48.50%
Performance Units [Member]
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense	12.7	11.9	14.2
Restricted stock activity
Granted, Number of Shares					187,450	224,735	230,245	333,685
Common Equity (Textuals)
Unrecognized total compensation costs related share based compensation	10.9
Months, on a weighted-average basis, expected for recognizing total compensation costs related to non-vested stock options	20 months
Intrinsic Value	11.6	13.1	17.1
Employee Service Share Based Compensation Tax Benefit Realized from Distribution of Shares	4.2	4.7	6.2
Stock Options [Member]
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense	3.6	3.8	2.6
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$30.07	$26.92
Non-Vested Options [Member]
Common Equity (Textuals)
Unrecognized total compensation costs related share based compensation	2
Months, on a weighted-average basis, expected for recognizing total compensation costs related to non-vested stock options	19 months
Restricted Stock [Member]
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense	2.1	1.6	2
Restricted stock activity
Outstanding	98,226			100,657	100,657	98,226			98,226
Granted, Number of Shares	51,873				43,212
Granted, Weighted-Average Market Price	$40.98
Released, Number of Shares	-46,228
Released, Weighted-Average Market Price	$34.31
Forfeited, Number of Shares	-3,214
Forfeited, Weighted-Average Market Price	$38.47
Outstanding	100,657	98,226
Common Equity (Textuals)
Unrecognized total compensation costs related share based compensation	2.1
Months, on a weighted-average basis, expected for recognizing total compensation costs related to non-vested stock options									20 months
Restricted stock vesting period in years					3 years
Intrinsic Value	2.3	2.8	2.2
Employee Service Share Based Compensation Tax Benefit Realized from Distribution of Shares	$0.90	$1.10	$0
Exercise Price, Range One [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$20.88
Exercise Price, Range One [Member] | Maximum [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$21.11
Exercise Price, Range One [Member] | Minimum [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$17.10
Exercise Price, Range Two [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$25.07
Exercise Price, Range Two [Member] | Maximum [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$29.35
Exercise Price, Range Two [Member] | Minimum [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$23.88
Exercise Price, Range Three [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$37.79
Exercise Price, Range Three [Member] | Maximum [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$41.03
Exercise Price, Range Three [Member] | Minimum [Member]
Common Equity (Textuals)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$34.88

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivatives Fair Value [Line Items]
Derivative, Asset	$12.60	$9
Derivative, Liability	7.3	0.3
Gains (losses)	17.2	11.4
Collateral Already Posted, Aggregate Fair Value	6.9	0
Other Deferred Charges and Other Assets [Member]
Derivatives Fair Value [Line Items]
Long-term portion of derivative assets	0.6
Other Long-Term Liabilities [Member]
Derivatives Fair Value [Line Items]
Long-term portion of derivative liabilities	0.7
Natural Gas [Member]
Derivatives Fair Value [Line Items]
Derivative, Asset	2.3	2.8
Derivative, Liability	7.1	0.1
Volume	21.4 million Dth	24.0 million Dth
Gains (losses)	4	-4
Fuel Oil [Member]
Derivatives Fair Value [Line Items]
Derivative, Asset	0	0.6
Derivative, Liability	0	0
Volume	9.2 million gallons	8.6 million gallons
Gains (losses)	0.5	0.5
FTRs [Member]
Derivatives Fair Value [Line Items]
Derivative, Asset	7	3.5
Derivative, Liability	0	0
Volume	26.1 million MWh	25.3 million MWh
Gains (losses)	12.7	14.9
Coal [Member]
Derivatives Fair Value [Line Items]
Derivative, Asset	3.3	2.1
Derivative, Liability	0.2	0.2
Derviative Instrument by Counterparty, Gross Amount Not Offset on Balance Sheet [Member] [Member]
Derivatives Fair Value [Line Items]
Derivative, Asset	-0.4	0
Derivative, Liability	-6.8	0
Collateral Already Posted, Aggregate Fair Value	$6.40	$0

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Assets:
Derivative, Asset	$12.60	$9
Total	12.6	9
Liabilities:
Derivative, Liability	7.3	0.3
Total	7.3	0.3
Fair Value, Inputs, Level 1 [Member]
Assets:
Derivative, Asset	0.4	3.2
Total	0.4	3.2
Liabilities:
Derivative, Liability	6.8	0
Total	6.8	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Derivative, Asset	5.2	2.3
Total	5.2	2.3
Liabilities:
Derivative, Liability	0.5	0.3
Total	0.5	0.3
Fair Value, Inputs, Level 3 [Member]
Assets:
Derivative, Asset	7	3.5
Total	7	3.5
Liabilities:
Derivative, Liability	0	0
Total	$0	$0

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of income tax expense
Current tax expense (benefit)	$31.20	$7.30	($1.40)
Deferred income taxes, net	192.5	194.7	195.2
Investment tax credit, net	-1.1	-1.1	-1.1
Total Income Tax Expense, Amount	222.6	200.9	192.7
The provision for income taxes for each of the years ended December 31 differs from the amount of income tax determined by applying the applicable U.S. statutory federal income tax rate to income before income taxes as a result of the following:
Expected tax at statutory federal tax rates, Amount	209.8	196.3	195.6
Expected tax at statutory federal tax rates, Effective Tax Rate	35.00%	35.00%	35.00%
State income taxes net of federal tax benefit, Amount	33	31.7	28.8
State income taxes net of federal tax benefit, Effective Tax Rate	5.50%	5.60%	5.10%
Production tax credits - wind, Amount	-17.4	-16.7	-15.9
Production tax credits - wind, Effective Tax Rate	-2.90%	-3.00%	-2.80%
Effective Tax Rate Reconciliation, 1603 Grant, Amount	-3.8	-7.4	0
Effective Tax Rate Reconciliation, 1603 Grant, Percent	-0.60%	-1.30%	0.00%
AFUDC - Equity, Amount	-1.5	-6.1	-12.2
AFUDC - Equity, Effective Tax Rate	-0.20%	-1.10%	-2.20%
Investment tax credit restored, Amount	-1.1	-1.1	-1.1
Investment tax credit restored, Effective Tax Rate	-0.20%	-0.20%	-0.20%
Domestic production activities deduction, Amount	0	0	-12.6
Domestic production activities deduction, Effective Tax Rate	0.00%	0.00%	-2.30%
Other, net, Amount	3.6	4.2	10.1
Other, net, Effective Tax Rate	0.50%	0.70%	1.80%
Total Income Tax Expense, Amount	222.6	200.9	192.7
Total Income Tax Expense, Effective Tax Rate	37.10%	35.70%	34.40%
Current
Deferred Tax Assets, Future Federal Tax Benefits, Current	56	113.1
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts	15.6	17.2
Employee benefits and compensation	11.6	11.7
Deferred Tax Asset Recoverable Gas Costs, Current	1	0.5
Other	2.3	3.3
Deferred Tax Assets, Net of Valuation Allowance, Current	86.5	145.8
Non-current
Deferred revenues	221.3	237
Employee benefits and compensation	92.1	92.4
Construction advances	15.5	15
Emission allowances	0.1	0
Other	31.7	42.2
Total Non-current Deferred Tax Assets	360.7	386.6
Total Deferred Tax Assets	447.2	532.4
Current
Prepaid items	39.8	70
Total Current Deferred Tax Liabilities	39.8	70
Non-current
Property-related	1,942.20	1,820.90
Employee benefits and compensation	131.2	135
Investment in transmission affiliate	164.1	147.8
Deferred transmission costs	58.5	50.8
Other	28.6	26.6
Total Non-current Deferred Tax Liabilities	2,324.60	2,181.10
Total Deferred Tax Liabilities	2,364.40	2,251.10
Consolidated Balance Sheet Presentation
Current Deferred Tax Asset	46.7	75.8
Non-Current Deferred Tax Liability	1,963.90	1,794.50
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance, January 1	8.4	10.8
Reductions for tax positions of prior years	-1.2	-2.4
Balance, December 31	7.2	8.4	10.8
Income Taxes (Textuals)
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0	0
Deferred tax assets valuation allowance	7.2	8.4
Accrued interest in the Consolidated Income Statements	0.3	0.2	0.2
Accrued penalties in the Consolidated Income Statements	0	0	0
Accrued interest on the Consolidated Balance Sheets	0.7	0.4
Accrued penalties on the Consolidated Balance Sheets	0	0
Operating Loss Carryforwards	3.9	216.8
Deferred Tax Assets, Operating Loss Carryforwards	1.4	75.9
Tax Credit Carryforward, Amount	54.6	37.2
Tax Credit Carryforward, Deferred Tax Asset	$54.60	$37.20

LongTerm_Debt_and_Capital_Leas2

Long-Term Debt and Capital Lease Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Megawatt
Long-term debt outstanding maturities and sinking fund requirements
Next year	$250
Year 2	0
Year 3	0
Year 4	250
Year 5	250
Thereafter	1,687
Total	2,437
Summary of capitalized leased facilities
Total Leased Facilities	2,215	2,279
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Issuance of long-term debt	250	250	250
Number of series of tax-exempt pollution control refunding bonds	2
Unsecured Long-term Debt, Noncurrent	147
Period of Power purchase contract with an unaffiliated independent power producer	25 years
Power capacity from a gas-fired cogeneration facility under capital lease (MW)	236
Minimum energy requirement in gas-fired cogeneration facility	0
Power purchase contract expiration year	31-Dec-22
Power purchase contract expected future renewable period	10 years
Total lease payment	411.9	407.7	400.8
Total capital lease obligation	2,712.50	2,712
Year 1	439.2
Year 2	455.4
Year 3	424.6
Year 4	425.4
Year 5	426.2
Thereafter	7,604.50
Total Minimum Lease Payments	9,775.30
Less: Estimated Executory Costs	-54.7
Net Minimum Lease Payments	9,720.60
Less: Interest	-6,902.50
Minimum Lease Payments	2,818.10
Less: Due Currently	-105.6
Capital lease obligations	2,712.50	2,712
Power Purchase Commitment [Member]
Summary of capitalized leased facilities
Capital Lease Asset	140.3	140.3
Accumulated amortization	-98.3	-92.5
Total Leased Facilities	42	47.8
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Total lease payment	34.9	33.7	32.5
Year 1	43.5
Year 2	45.1
Year 3	13.9
Year 4	14.7
Year 5	15.5
Thereafter	41.3
Total Minimum Lease Payments	174
Less: Estimated Executory Costs	-54.7
Net Minimum Lease Payments	119.3
Less: Interest	-34.8
Minimum Lease Payments	84.5
Less: Due Currently	-24.6
Capital lease obligations	59.9
PWGS Units 1 and 2 [Member]
Summary of capitalized leased facilities
Capital Lease Asset	682.7	681.5
Accumulated amortization	-217.6	-190.1
Total Leased Facilities	465.1	491.4
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Period of Power purchase contract with an unaffiliated independent power producer	25 years
Total lease payment	99.2	99.1	99
Capital lease obligation at the end of life of contract	0
Year 1	99.3
Year 2	99.3
Year 3	99.3
Year 4	99.3
Year 5	99.3
Thereafter	1,184.70
Total Minimum Lease Payments	1,681.20
Less: Estimated Executory Costs	0
Net Minimum Lease Payments	1,681.20
Less: Interest	-1,044.10
Minimum Lease Payments	637.1
Less: Due Currently	-10.2
Capital lease obligations	626.9
PWGS 1 [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Estimated Total Increase In Regulatory Asset due to Minimum Lease Payment, Over Life of Contract	129.1
Power capacity from a gas-fired cogeneration facility under capital lease (MW)	545
Increase In Regulatory Asset Due To Minimum Lease Payment, End Date of Increase	31-Dec-21
PWGS 2 [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Estimated Total Increase In Regulatory Asset due to Minimum Lease Payment, Over Life of Contract	127.9
Power capacity from a gas-fired cogeneration facility under capital lease (MW)	545
Increase In Regulatory Asset Due To Minimum Lease Payment, End Date of Increase	31-Dec-24
Oak Creek Expansion [Member]
Summary of capitalized leased facilities
Capital Lease Asset	2,025.60	1,991.10
Accumulated amortization	-317.7	-251.3
Total Leased Facilities	1,707.90	1,739.80
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Period of Power purchase contract with an unaffiliated independent power producer	30 years
Total lease payment	277.8	274.9	269.3
Regulatory asset value at the end of life of contract	0
Capital lease obligation at the end of life of contract	0
Year 1	296.4
Year 2	311
Year 3	311.4
Year 4	311.4
Year 5	311.4
Thereafter	6,378.50
Total Minimum Lease Payments	7,920.10
Less: Estimated Executory Costs	0
Net Minimum Lease Payments	7,920.10
Less: Interest	-5,823.60
Minimum Lease Payments	2,096.50
Less: Due Currently	-70.8
Capital lease obligations	2,025.70
OC 1 [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Estimated Total Increase In Regulatory Asset due to Minimum Lease Payment, Over Life of Contract	537.6
Increase In Regulatory Asset Due To Minimum Lease Payment, End Date of Increase	31-May-29
OC 2 [Member]
Long-Term Debt and Capital Lease Obligations (Textuals) [Abstract]
Estimated Total Increase In Regulatory Asset due to Minimum Lease Payment, Over Life of Contract	$442
Increase In Regulatory Asset Due To Minimum Lease Payment, End Date of Increase	31-Jan-30

Preferred_Stock_Details

Preferred Stock (Details) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Preferred stock	$30.40	$30.40
Serial preferred stock, $25 par value; authorized 5,000,000 shares; none outstanding [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	5,000,000	5,000,000
Preferred Stock, Shares Outstanding	0	0
Preferred Stock, Redemption Price Per Share	$0	$0
Preferred stock	0	0
Preferred Stock, Par or Stated Value Per Share	$25	$25
Serial preferred stock, 3.60% Series Redeemable [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	260,000	260,000
Preferred Stock, Redemption Price Per Share	$101	$101
Preferred stock	26	26
Preferred Stock, Dividend Rate, Percentage	3.60%	3.60%
Preferred Stock, Par or Stated Value Per Share	$100	$100
Six Per Cent. Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	45,000	45,000
Preferred Stock, Shares Outstanding	44,498	44,498
Preferred Stock, Redemption Price Per Share	$0	$0
Preferred stock	$4.40	$4.40
Preferred Stock, Dividend Rate, Percentage	6.00%	6.00%
Preferred Stock, Par or Stated Value Per Share	$100	$100
Serial preferred stock, $100 par value; authorized 2,286,500 shares [Member] [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	2,286,500	2,286,500
Preferred Stock, Par or Stated Value Per Share	$100	$100

Regulatory_Assets_and_Liabilit2

Regulatory Assets and Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Regulatory Assets [Line Items]
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided	$11.70
Regulatory assets earning a return based on short-term rates	115.1
Regulatory Assets
Regulatory Assets	1,626.90	1,370.30
Deferred unrecognized pension costs [Member]
Regulatory Assets
Regulatory Assets	482.8	393
Deferred income tax related [Member]
Regulatory Assets
Regulatory Assets	171.5	165.8
Escrowed electric transmission costs [Member]
Regulatory Assets
Regulatory Assets	146	126.8
Deferred plant related -- capital lease [Member]
Regulatory Assets
Regulatory Assets	603	512.5
Other, net [Member]
Regulatory Assets
Regulatory Assets	$223.60	$172.20

Related_Parties_Details

Related Parties (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments	$57.90	$60.20	$57.60
Distributions from transmission affiliate	50.5	47.8	46.1
We Power [Member]
Provided and received services from the associated companies
Services Received	389	381.7	375.3
Wisconsin Gas [Member]
Provided and received services from the associated companies
Services Received	20.6	23.6	16.6
Wisconsin Energy [Member]
Provided and received services from the associated companies
Services Received	15.2	10.2	23.9
American Transmission Company [Member]
Related Party Transaction [Line Items]
Equity Method Investment, Summarized Financial Information, Revenue	635	626.3	603.3
Equity Method Investment, Summarized Financial Information, Operating Income	327.6	331.3	322.2
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	238.7	247.6	237.4
Equity Method Investment, Summarized Financial Information, Current Assets	66.4	80.7	63.1
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	3,728.70	3,509.50	3,274.70
Equity Method Investment, Summarized Financial Information, Current Liabilities	313.1	381.5	251.5
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities	1,864.80	1,676.20	1,645.80
Provided and received services from the associated companies
Services Received	231.4	234.2	222.7
Receivable and payable balances with ATC
Services Received, -ATC	19.3	19.5
Related Parties (Textuals) [Abstract]
Equity interest in ATC	23.00%
Services [Member] | We Power [Member]
Provided and received services from the associated companies
Services Provided	41.5	2.8	2.3
Services [Member] | Wisconsin Gas [Member]
Provided and received services from the associated companies
Services Provided	81.7	83.4	78.7
Services [Member] | Wisconsin Energy [Member]
Provided and received services from the associated companies
Services Provided	11.3	5.6	5.6
Services [Member] | Other Affiliates [Member]
Provided and received services from the associated companies
Services Provided	1.5	1.6	1.2
Services [Member] | American Transmission Company [Member]
Provided and received services from the associated companies
Services Provided	8.1	9	8.2
Receivable and payable balances with ATC
Services Provided, -ATC	$0.60	$0.60

Segment_Reporting_Details

Segment Reporting (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Financial information of reportable operating segments
Operating Revenues	$4,059.40	[1]	$3,800.20	[1]	$3,613.30	[1]
Depreciation and Amortization	295.7		278.6		257.6
Operating Income (Loss)	650.4	[2]	605.9	[2]	583.3	[2]
Equity in Earnings of Transmission Affiliate	57.9		60.2		57.6
Payments to Acquire Property, Plant, and Equipment	540.9		506.9		575.8
Electric [Member]
Financial information of reportable operating segments
Operating Revenues	3,401.10	[1]	3,308.70	[1]	3,193.90	[1]
Depreciation and Amortization	261.5		249.5		230.3
Operating Income (Loss)	565.6	[2]	533.2	[2]	536.5	[2]
Equity in Earnings of Transmission Affiliate	57.9		60.2		57.6
Payments to Acquire Property, Plant, and Equipment	470.2		438.5		524.9
Gas [Member]
Financial information of reportable operating segments
Operating Revenues	614.2	[1]	451.9	[1]	385.1	[1]
Depreciation and Amortization	30.5		25.5		23.9
Operating Income (Loss)	77.2	[2]	69.8	[2]	50	[2]
Equity in Earnings of Transmission Affiliate	0		0		0
Payments to Acquire Property, Plant, and Equipment	67.9		57.8		50.8
Steam [Member]
Financial information of reportable operating segments
Operating Revenues	44.1	[1]	39.6	[1]	34.3	[1]
Depreciation and Amortization	3.7		3.6		3.4
Operating Income (Loss)	7.6	[2]	2.9	[2]	-3.2	[2]
Equity in Earnings of Transmission Affiliate	0		0		0
Payments to Acquire Property, Plant, and Equipment	2.8		10.6		0
All Other Segments [Member]
Financial information of reportable operating segments
Operating Revenues	0	[1],[3]	0	[1],[3]	0	[1],[3]
Depreciation and Amortization	0	[3]	0	[3]	0	[3]
Operating Income (Loss)	0	[2],[3]	0	[2],[3]	0	[2],[3]
Equity in Earnings of Transmission Affiliate	0	[3]	0	[3]	0	[3]
Payments to Acquire Property, Plant, and Equipment	$0	[3]	$0	[3]	$0.10	[3]
[1]	We account for intersegment revenues at a tariff rate established by the PSCW. Intersegment revenues were not material.
[2]	We evaluate operating income to manage our utility business. Equity in Earnings of Transmission Affiliate, Interest Expense and Income Taxes are not included in segment operating income.
[3]	Other includes primarily non-utility property and investments, materials and supplies, deferred charges and other corporate items.

ShortTerm_Debt_Details

Short-Term Debt (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Commercial Paper	$306.80	$174.50
Short-Term Debt (Textuals) [Abstract]
Undrawn lines under bank back-up credit facilities	494.9
Short-term debt outstanding supported by the available lines of credit	306.8
Note Payable from Subsidiary to Wisconsin Energy	22.4
Note payable from Subsidiary to Wisconsin Energy, weighted-average interest rate	6.75%
Wisconsin Electric [Member]
Short-Term Debt (Textuals) [Abstract]
Minimum total funded debt to capitalization ratio	65.00%
Commercial Paper [Member]
Short-term notes payable balances and their corresponding weighted-average interest rates
Commercial paper, weighted-average interest rate	0.25%	0.22%
Commercial paper [Abstract]
Maximum Short-Term Debt Outstanding	401	354.5
Average Short-Term Debt Outstanding	$179.50	$98
Weighted-Average Interest Rate	0.22%	0.22%

Benefits_Details_1

Benefits (Details 1) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Current pension plan asset allocation in real estate investments					10.00%
Current pension plan asset allocation in equity investments	45.00%				35.00%
Current pension plan asset allocation in fixed income investments	55.00%				55.00%
Amounts recognized in Consolidated Balance Sheets
Other long-term liabilities	$254,500,000	$160,100,000
Pension Plans [Member]
Change in Plan Assets
Fair Value at January 1	1,168,900,000	1,121,100,000
Actual earnings (loss) on plan assets	71,200,000	119,000,000
Employer contributions	7,200,000	7,500,000
Participants' contributions	0	0
Gross benefits paid	-87,300,000	-78,700,000
Fair Value at December 31	1,160,000,000	1,168,900,000
Amounts recognized in Consolidated Balance Sheets
Other deferred charges	0	34,300,000
Other long-term liabilities	155,200,000	88,500,000
Net Liability	155,200,000	54,200,000
Amounts not yet been recognized in net periodic benefit cost
Net actuarial loss	476,400,000	384,700,000
Prior service costs (credits)	6,300,000	8,300,000
Total	482,700,000	393,000,000
Defined Benefit Plan, Plan Amendments	0	-900,000
OPEB [Member]
Change in Plan Assets
Fair Value at January 1	222,400,000	194,800,000
Actual earnings (loss) on plan assets	12,000,000	30,700,000
Employer contributions	3,200,000	10,100,000	13,600,000
Participants' contributions	8,400,000	8,100,000
Gross benefits paid	-21,100,000	-21,300,000
Fair Value at December 31	224,900,000	222,400,000	194,800,000
Amounts recognized in Consolidated Balance Sheets
Other deferred charges	1,900,000	1,600,000
Other long-term liabilities	99,300,000	71,600,000
Net Liability	97,400,000	70,000,000
Amounts not yet been recognized in net periodic benefit cost
Net actuarial loss	20,700,000	-7,600,000
Prior service costs (credits)	-5,200,000	-1,700,000
Total	15,500,000	-9,300,000
Defined Benefit Plan, Plan Amendments	-5,200,000	0
Pension, Qualified [Member] | Pension Plans [Member]
Change in Plan Assets
Employer contributions	0	0	88,500,000	100,000,000
Fair Value, Inputs, Level 2 [Member] | Pension Plans [Member]
Change in Plan Assets
Fair Value at December 31	539,900,000	465,500,000
Fair Value, Inputs, Level 2 [Member] | OPEB [Member]
Change in Plan Assets
Fair Value at December 31	82,200,000	71,200,000
Private Placement [Member] | Pension Plans [Member]
Change in Plan Assets
Fair Value at December 31	9,300,000
Private Placement [Member] | OPEB [Member]
Change in Plan Assets
Fair Value at December 31	700,000
Private Placement [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plans [Member]
Change in Plan Assets
Fair Value at December 31	$0

Common_Equity_Details_1

Common Equity (Details 1) (USD $)	1 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Jan. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock option activity
Outstanding, Shares, Beginning Balance	6,450,277
Outstanding, Weighted-Average Exercise Price, Beginning	$30.07
Granted, shares	495,550
Granted, Weighted-Average Exercise Price		$4.18	$3.45	$3.34
Outstanding, Shares, Ending Balance		6,450,277
Outstanding, Weighted-Average Exercise Price, Ending		$30.07
Exercisable, shares		3,682,442
Exercisable, Weighted-Average Exercise Price		$24.14
Stock Options [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures		864,860
Stock option activity
Outstanding, Shares, Beginning Balance		7,688,843
Outstanding, Weighted-Average Exercise Price, Beginning		$26.92
Granted, Weighted-Average Exercise Price		$41.03
Exercised, shares		-2,086,231
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price		$22.95
Forfeited, shares		-17,195
Forfeited, Weighted-Average Exercise Price		$37.42
Outstanding, Shares, Ending Balance		6,450,277
Outstanding, Weighted-Average Exercise Price, Ending		$30.07
Outstanding, Weighted-Average Remaining Contractual Life (Years)		5 years 8 months
Outstanding, Aggregate Intrinsic Value		$146.20
Exercisable, shares		3,682,442
Exercisable, Weighted-Average Exercise Price		$24.14
Exercisable, Weighted-Average Remaining Contractual Life (Years)		3 years 11 months
Exercisable, Aggregate Intrinsic Value		$105.30
Exercise Price, Range One [Member]
Stock option activity
Outstanding, Shares, Ending Balance		1,411,769
Outstanding, Weighted-Average Exercise Price, Ending		$20.88
Exercisable, shares		1,411,769
Exercisable, Weighted-Average Exercise Price		$20.88
Exercise Price, Range Two [Member]
Stock option activity
Outstanding, Shares, Ending Balance		2,038,633
Outstanding, Weighted-Average Exercise Price, Ending		$25.07
Exercisable, shares		2,038,633
Exercisable, Weighted-Average Exercise Price		$25.07
Exercise Price, Range Three [Member]
Stock option activity
Outstanding, Shares, Ending Balance		2,999,875
Outstanding, Weighted-Average Exercise Price, Ending		$37.79
Exercisable, shares		232,040
Exercisable, Weighted-Average Exercise Price		$35.86
Minimum [Member] | Exercise Price, Range One [Member]
Stock option activity
Outstanding, Weighted-Average Exercise Price, Ending		$17.10
Minimum [Member] | Exercise Price, Range Two [Member]
Stock option activity
Outstanding, Weighted-Average Exercise Price, Ending		$23.88
Minimum [Member] | Exercise Price, Range Three [Member]
Stock option activity
Outstanding, Weighted-Average Exercise Price, Ending		$34.88
Maximum [Member] | Exercise Price, Range One [Member]
Stock option activity
Outstanding, Weighted-Average Exercise Price, Ending		$21.11
Maximum [Member] | Exercise Price, Range Two [Member]
Stock option activity
Outstanding, Weighted-Average Exercise Price, Ending		$29.35
Maximum [Member] | Exercise Price, Range Three [Member]
Stock option activity
Outstanding, Weighted-Average Exercise Price, Ending		$41.03

Derivative_Instruments_Details1

Derivative Instruments (Details 1) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Regulatory Assets [Line Items]
Regulatory assets related to derivatives	$1,626.90	$1,370.30
Derivative [Member]
Regulatory Assets [Line Items]
Regulatory assets related to derivatives	$8.40	$0.30

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 1) (Derivative [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Member]
Fair value of derivatives classified as Level 3 in the fair value hierarchy
Begninning Balance	$3.50	$4.70
Realized and unrealized gains (losses)	0	0
Purchases	15.6	10.6
Issuances	0	0
Settlements	-12.1	-11.8
Transfers in and/or out of Level 3	0	0
Ending Balance	$7	$3.50

Regulatory_Assets_and_Liabilit3

Regulatory Assets and Liabilities (Details 1) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Regulatory Liabilities [Line Items]
Regulatory liabilities	$615.90	$634.20
Deferred cost of removal obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	571.2	558.9
Other, net [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$44.70	$75.30

Recovered_Sheet1

Summary Of Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Public Utility Property Plant And Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.90%	2.90%	2.90%
Regulatory liabilities	$615.90	$634.20
AFUDC - Debt	1.8	7.4	14.5
AFUDC - Equity	4.4	17.6	34.9
Asset Retirement Obligation Costs [Member]
Public Utility Property Plant And Equipment [Line Items]
Regulatory liabilities	$571.20	$558.90

Benefits_Details_2

Benefits (Details 2) (USD $)	12 Months Ended				1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015	Jan. 31, 2015	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Matching contributions under Savings Plans	$13,000,000	$13,000,000	$12,500,000
A one-percentage-point change in assumed health care cost trend rates effects
1% Increase, in assumed health care cost trend rates, Effect on, Post-retirement benefit obligation	29,300,000
1% Decrease, in assumed health care cost trend rates, Effect on, Post-retirement benefit obligation	-24,400,000
1% Increase, in assumed health care cost trend rates, Effect on, Total of service and interest cost components	3,100,000
1% Decrease, in assumed health care cost trend rates, Effect on, Total of service and interest cost components	-2,500,000
Benefits (Textuals) [Abstract]
Health care cost trend rate up to specified age	65
Health care cost trend rate post specified age	65
Current pension plan target asset allocation in equity investments	45.00%					35.00%
Current pension plan target asset allocation in fixed income investments	55.00%					55.00%
Other Post-Retirement Employee Benefits target asset allocation in equity investments						60.00%
Other Post-Retirement Employee Benefits target asset allocation in fixed income investments						40.00%
Matching contributions under Savings Plans	13,000,000	13,000,000	12,500,000
Postemployment benefits liability	1,800,000	2,800,000
Pension, Qualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	1,314,300,000	1,222,300,000
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amortization of Previously Unrecognized Benefit Costs				38,000,000
Net Periodic Benefit Cost
Service cost	9,400,000	13,900,000	19,800,000
Interest cost	59,300,000	52,400,000	56,800,000
Expected return on plan assets	-79,100,000	-77,200,000	-71,800,000
Amortization of:
Transition obligation	0	0	0
Prior service cost (credit)	2,000,000	2,200,000	2,100,000
Actuarial loss	26,900,000	41,700,000	30,600,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	0	1,500,000	0
Defined Benefit Plan, Other Changes	0	0	400,000
Net Periodic Benefit Cost	18,500,000	34,500,000	37,900,000
Weighted-Average assumptions used to determine benefit obligations as of Dec. 31
Discount rate	4.15%	5.00%	4.10%
Rate of compensation increase	4.00%	4.00%	4.00%
Weighted-Average assumptions used to determine net cost for year ended Dec. 31
Discount rate	5.00%	4.10%	5.05%
Expected return on plan assets	7.25%	7.25%	7.25%
Rate of compensation increase	4.00%	4.00%	4.00%
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,160,000,000	1,168,900,000	1,121,100,000
Employer contributions to defined benefit plan
Employer contributions	7,200,000	7,500,000
Expected benefit payments in future
2012	91,800,000
2013	91,500,000
2014	92,100,000
2015	89,500,000
2016	89,400,000
2017-2021	429,500,000
Pension Plans [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	610,800,000	703,400,000
Pension Plans [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	539,900,000	465,500,000
Pension Plans [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	9,300,000	0
Pension Plans [Member] | Cash And Cash Equivalents [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	5,100,000	16,900,000
Pension Plans [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	5,100,000	16,900,000
Pension Plans [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | U.S. Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	404,500,000	418,500,000
Pension Plans [Member] | U.S. Equity [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	404,500,000	418,500,000
Pension Plans [Member] | U.S. Equity [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | U.S. Equity [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | International Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	127,200,000	146,600,000
Pension Plans [Member] | International Equity [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	103,300,000	117,800,000
Pension Plans [Member] | International Equity [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	23,900,000	28,800,000
Pension Plans [Member] | International Equity [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | U.S. Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	515,400,000	494,300,000
Pension Plans [Member] | U.S. Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	34,200,000	87,300,000
Pension Plans [Member] | U.S. Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	481,200,000	407,000,000
Pension Plans [Member] | U.S. Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | International Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	98,500,000	92,600,000
Pension Plans [Member] | International Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	63,700,000	62,900,000
Pension Plans [Member] | International Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	34,800,000	29,700,000
Pension Plans [Member] | International Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
Pension Plans [Member] | Private Placement [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	9,300,000
Pension Plans [Member] | Private Placement [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
Pension Plans [Member] | Private Placement [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
Pension Plans [Member] | Private Placement [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	9,300,000
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amortization of Previously Unrecognized Benefit Costs				-200,000
Net Periodic Benefit Cost
Service cost	8,100,000	9,500,000	9,800,000
Interest cost	14,400,000	12,700,000	16,700,000
Expected return on plan assets	-16,200,000	-14,500,000	-13,000,000
Amortization of:
Transition obligation	0	0	300,000
Prior service cost (credit)	-1,700,000	-1,900,000	-1,900,000
Actuarial loss	200,000	1,500,000	5,000,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	0	0	0
Defined Benefit Plan, Other Changes	0	0	0
Net Periodic Benefit Cost	4,800,000	7,300,000	16,900,000
Weighted-Average assumptions used to determine benefit obligations as of Dec. 31
Discount rate	4.20%	4.95%	4.15%
Weighted-Average assumptions used to determine net cost for year ended Dec. 31
Discount rate	4.95%	4.15%	5.20%
Expected return on plan assets	7.50%	7.50%	7.50%
Assumed health care cost trend rates as of Dec. 31
Health care cost trend rate assumed for next year, Pre 65	0.075	0.075	0.075
Health care cost trend rate assumed for next year, Post 65	0.075	0.075	0.075
Rate that the cost trend rate gradually adjusts to	0.05	0.05	0.05
Year that the rate reaches the rate it is assumed to remain at (Pre 65 / Post 65)	2021/2021	2021/2021	2017/2017
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	224,900,000	222,400,000	194,800,000
Employer contributions to defined benefit plan
Employer contributions	3,200,000	10,100,000	13,600,000
Expected benefit payments in future
2012	13,900,000
2013	14,800,000
2014	16,000,000
2015	17,100,000
2016	18,200,000
2017-2021	99,300,000
OPEB [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	142,000,000	151,200,000
OPEB [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	82,200,000	71,200,000
OPEB [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	700,000	0
OPEB [Member] | Cash And Cash Equivalents [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	900,000	1,800,000
OPEB [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	900,000	1,800,000
OPEB [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | U.S. Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	98,400,000	100,500,000
OPEB [Member] | U.S. Equity [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	98,400,000	100,500,000
OPEB [Member] | U.S. Equity [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | U.S. Equity [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | International Equity [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	30,200,000	33,700,000
OPEB [Member] | International Equity [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	28,500,000	31,800,000
OPEB [Member] | International Equity [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	1,700,000	1,900,000
OPEB [Member] | International Equity [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | U.S. Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	78,200,000	71,100,000
OPEB [Member] | U.S. Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	2,400,000	5,700,000
OPEB [Member] | U.S. Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	75,800,000	65,400,000
OPEB [Member] | U.S. Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | International Bonds [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	16,500,000	15,300,000
OPEB [Member] | International Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	11,800,000	11,400,000
OPEB [Member] | International Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	4,700,000	3,900,000
OPEB [Member] | International Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0	0
OPEB [Member] | Private Placement [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	700,000
OPEB [Member] | Private Placement [Member] | Fair Value, Inputs, Level 1 [Member]
Summary of fair value of pension plan assets by asset category within the fair value hierarchy
Fair value of our pension plan assets	0
Pension, Qualified [Member] | Pension Plans [Member]
Employer contributions to defined benefit plan
Employer contributions	0	0	88,500,000		100,000,000
Pension, Non-Qualified [Member] | Pension Plans [Member]
Employer contributions to defined benefit plan
Employer contributions	$7,200,000	$7,500,000	$6,000,000

Common_Equity_Details_2

Common Equity (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014
Stock options outstanding
Options Outstanding, Number, Total	6,450,277
Options Outstanding, Weighted-Average Exercise Price	$30.07
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 8 months
Options Exercisable, Number, Total	3,682,442
Options Exercisable, Weighted-Average Exercise Price	$24.14
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	3 years 11 months
Exercise Price, Range One [Member]
Stock options outstanding
Options Outstanding, Number, Total	1,411,769
Options Outstanding, Weighted-Average Exercise Price	$20.88
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 years 7 months
Options Exercisable, Number, Total	1,411,769
Options Exercisable, Weighted-Average Exercise Price	$20.88
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	3 years 7 months
Exercise Price, Range One [Member] | Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$21.11
Exercise Price, Range One [Member] | Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$17.10
Exercise Price, Range Two [Member]
Stock options outstanding
Options Outstanding, Number, Total	2,038,633
Options Outstanding, Weighted-Average Exercise Price	$25.07
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 years 8 months
Options Exercisable, Number, Total	2,038,633
Options Exercisable, Weighted-Average Exercise Price	$25.07
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	3 years 8 months
Exercise Price, Range Two [Member] | Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$29.35
Exercise Price, Range Two [Member] | Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$23.88
Exercise Price, Range Three [Member]
Stock options outstanding
Options Outstanding, Number, Total	2,999,875
Options Outstanding, Weighted-Average Exercise Price	$37.79
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	8 years 0 months
Options Exercisable, Number, Total	232,040
Options Exercisable, Weighted-Average Exercise Price	$35.86
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	7 years 5 months
Exercise Price, Range Three [Member] | Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$41.03
Exercise Price, Range Three [Member] | Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$34.88

Derivative_Instruments_Details2

Derivative Instruments (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Regulatory Liabilities [Line Items]
Regulatory liabilities related to derivatives	$615.90	$634.20
Derivative [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities related to derivatives	$12.20	$8.10

Fair_Value_Measurements_Detail2

Fair Value Measurements (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Financial Instruments
Preferred Stock	$30.40	$30.40
Long-term debt including current portion, carrying value	2,437	2,487
Long-term debt including current portion, fair value	2,759.60	2,634.70
Fair Value [Member]
Financial Instruments
Preferred Stock	27.1	26
Carrying Amount [Member]
Financial Instruments
Preferred Stock	$30.40	$30.40

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details 1)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.90%	2.90%	2.90%
ATC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	23.00%	23.00%
Voting rights in ATC board members	one out of ten
Number of votes with each member of ATC	1
Maximum voting control for individual member in ATC	10.00%

Common_Equity_Details_3

Common Equity (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Non-vested options
Granted, Weighted-Average Exercise Price	$4.18	$3.45	$3.34
Outstanding, Shares, Ending Balance	6,450,277
Outstanding, Weighted-Average Exercise Price, Ending	$30.07
Non-Vested Options [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$3.65	$3.38
Non-vested options
Outstanding, Shares, Beginning Balance	2,289,400
Granted, shares	864,860
Granted, Weighted-Average Exercise Price	$4.18
Vested, shares	-369,230
Vested, Weighted-Average Exercise Price	$3.26
Forfeited, shares	-17,195
Forfeited, Weighted-Average Exercise Price	$3.56
Outstanding, Shares, Ending Balance	2,767,835

Derivative_Instruments_Details3

Derivative Instruments (Details 3) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value	$6.90	$0
Derivative Asset	12.6	9
Derivative Liability	7.3	0.3
Interest Expense, net	116.5	121.4	113.2
Derviative Instrument by Counterparty, Gross Amount Recognized on Balance Sheet [Member]
Derivative [Line Items]
Derivative Asset	12.6	9
Derivative Liability	7.3	0.3
Derviative Instrument by Counterparty, Gross Amount Not Offset on Balance Sheet [Member] [Member]
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value	6.4	0
Derivative Asset	-0.4	0
Derivative Liability	-6.8	0
Derviative Instrument by Counterparty, Net Amount [Member]
Derivative [Line Items]
Derivative Asset	12.2	9
Derivative Liability	$0.50	$0.30

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015
Fair value of stock options
Dividend yield	3.80%	3.70%	3.90%
Expected volatility	18.00%	18.00%	19.00%
Expected life (years)	5 years 10 months	5 years 11 months	5 years 11 months
Expected forfeiture rate	2.00%	2.00%	2.00%
Weighted average fair value of our stock options granted	$4.18	$3.45	$3.34
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration of options from time of grant				10 years
Fair value of stock options
Weighted average fair value of our stock options granted	$41.03
Maximum [Member]
Fair value of stock options
Risk-free interest rate	3.00%	1.90%	2.00%
Minimum [Member]
Fair value of stock options
Risk-free interest rate	0.10%	0.10%	0.10%

Common_Equity_Details_4

Common Equity (Details 4) (USD $)	12 Months Ended				1 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015
Common Equity (Textuals)
Common stock shares, Outstanding		33,289,327	33,289,327
Exercise price of non qualified stock options	$52.90
Intrinsic value of options exercised		$47.50	$41.20	$42.90
Exercise price of the stock option on the grant date	no less than 100% of the common stock's fair market value
Minimum percentage award based on performance unit		0
Maximum percentage award based on performance unit		1.75
Exercise of stock options		$47.90	$45.50	$45.40
Ability to declare common dividends limited to Percentage of Net Income by Wisconsin Electric		limited to 75% or 50%
Wisconsin Electric's common stock equity to total capitalization		less than 25% and 20%
3.60% Serial Preferred Stock		3.60%
Stock Options [Member]
Common Equity (Textuals)
Mimimum period after grant that stock options can be exercised	6 months
Expiration of options from time of grant	10 years
Restricted Stock [Member]
Common Equity (Textuals)
Option grants vesting period in years					3 years

Summary_of_Signfificant_Accoun

Summary of Signfificant Accounting Policies (Details 3) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Subsidiary or Equity Method Investee [Line Items]
Assets	$12,646.70	$12,285.60
Symmetrical Fuel Cost Tolerance Range Set By Regulatory Authority	Our retail electric rates in Wisconsin are established by the PSCW and include base amounts for fuel and purchased power costs. The electric fuel rules in Wisconsin allow us to defer, for subsequent rate recovery or refund, any under-collection or over-collection of fuel costs that are outside of the symmetrical fuel cost tolerance, which the PSCW set at plus or minus 2% of the approved fuel cost plan. The deferred under-collected amounts are subject to an excess revenues test. Our retail gas rates include monthly adjustments which permit the recovery or refund of actual purchased gas costs. We defer any difference between actual gas costs incurred (adjusted for a sharing mechanism) and costs recovered through rates as a current asset or liability. The deferred balance is returned to or recovered from customers at intervals throughout the year.
Fuel Cost Tolerance Range Set by Regulators, Percent	2.00%
Other Income and Deductions, Net
AFUDC - Equity	4.4	17.6	34.9
Gain on Property Sales	4.3	0.8	0.3
Other, net	0	-1	-2.9
Other Income and Deductions, net	8.7	17.4	32.3
Inventories
Fossil Fuel	125.5	117.5
Materials and Supplies	145	129.5
Natural Gas in Storage	50	34
Total	320.5	281
Minimum duration to recover outstanding regulatory assets	1 year
Maximum duration to recover outstanding regulatory assets	8 years
Debt Securities In Cash Equivalents, Maximum Period Until Maturity	0 years 3 months
Disposal Group, Including Discontinued Operation, Long Lived Assets	0
Treasury Grant	17.4	48	0
Grant Revenue Received	76.2
Subsidiaries [Member]
Subsidiary or Equity Method Investee [Line Items]
Assets	$28.40	$29.10

Subsequent_Event_Details

Subsequent Event (Details) (Subsequent Event [Member], USD $)	Jan. 12, 2015
In Millions, unless otherwise specified
Subsequent Event [Member]
Subsequent Event [Line Items]
Unrecovered plant costs to be sought from customers	$190
Carrying value of Michigan assets to be sold	$292

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$39.70	$36.70	$36.90
Expense	31.3	31.4	8.7
Deferral	10	2.7	20.7
Net Write-offs	-34.2	-31.1	-29.6
Balance at End of Period	$46.80	$39.70	$36.70