Wisconsin Electric Power Company PFD 3.60% (WELPP) 10-Q 1 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document (USD $)	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013
Entity Information [Line Items]	'	'
Entity Registrant Name	'WISCONSIN ELECTRIC POWER CO	'
Entity Central Index Key	'0000107815	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
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	'	$27

Consolidated_Condensed_Income_

Consolidated Condensed Income Statements (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating Revenues	$964.60	$951.90	$2,849.70	$2,739.10
Operating Expenses	'	'	'	'
Fuel and purchased power	340.4	337.7	890.1	852.8
Cost of gas sold	24.4	22	184.1	154.1
Other operation and maintenance	338	305.7	1,023.10	959.7
Depreciation and amortization	69.5	65	207.4	190
Property and revenue taxes	27.7	28.2	83.1	84.6
Total Operating Expenses	800	758.6	2,387.80	2,241.20
Operating Income	164.6	193.3	461.9	497.9
Equity in earnings of transmission affiliate	15.1	15	44.9	43
Other Income, net	4.6	8.8	14.1	32.7
Interest Expense, net	29.3	27.5	91.5	80.7
Income Before Income Taxes	155	189.6	429.4	492.9
Income Tax Expense	55.8	67.1	152.4	171.2
Net Income	99.2	122.5	277	321.7
Preferred Stock Dividend Requirement	0.3	0.3	0.9	0.9
Earnings Available for Common Stockholder	$98.90	$122.20	$276.10	$320.80

Consolidated_Condensed_Balance

Consolidated Condensed Balance Sheets (Unaudited) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Property, Plant and Equipment	'	'
In service	$9,764.10	$9,568.90
Accumulated depreciation	-3,223.70	-3,117
Property, Plant and Equipment in Service, Net	6,540.40	6,451.90
Construction work in progress	379.5	289.1
Leased facilities, net	2,303.90	2,340.20
Net Property, Plant and Equipment	9,223.80	9,081.20
Investments	'	'
Equity investment in transmission affiliate	348.8	332.6
Other	0.2	0.3
Total Investments	349	332.9
Current Assets	'	'
Cash and cash equivalents	17.1	34.1
Accounts receivable, net	261.1	226.3
Accounts receivable from related parties	14.3	6.1
Accrued revenues	149.8	213.8
Materials, supplies and inventories	299	312.2
Deferred Tax Assets, Net, Current	81.3	4.1
Prepayments and other	140.4	197.4
Total Current Assets	963	994
Deferred Charges and Other Assets	'	'
Regulatory assets	1,472	1,452.20
Other	147	162.3
Total Deferred Charges and Other Assets	1,619	1,614.50
Total Assets	12,154.80	12,022.60
Capitalization	'	'
Common equity	3,426.90	3,366.40
Preferred stock	30.4	30.4
Long-term debt	2,166.80	2,216.70
Capital lease obligations	2,719.50	2,703.10
Total Capitalization	8,343.60	8,316.60
Current Liabilities	'	'
Long-term debt and capital lease obligations due currently	373.7	357
Short-term debt	26.5	105.5
Subsidiary note payable to Wisconsin Energy	22.8	23.4
Accounts payable	254.4	306.8
Accounts payable to related parties	84.2	93.4
Accrued payroll and benefits	83.3	75.4
Other	130.3	110.2
Total Current Liabilities	975.2	1,071.70
Deferred Credits and Other Liabilities	'	'
Regulatory liabilities	585	600.3
Deferred income taxes - long term	1,750.20	1,533.60
Pension and other benefit obligations	284.2	189.2
Other	216.6	311.2
Total Deferred Credits and Other Liabilities	2,836	2,634.30
Total Capitalization and Liabilities	$12,154.80	$12,022.60

Consolidated_Condensed_Stateme

Consolidated Condensed Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Operating Activities	'	'
Net Income	$277	$321.70
Reconciliation to cash	'	'
Depreciation and amortization	214.1	196.7
Deferred income taxes and investment tax credits, net	145.5	211.3
Contributions to qualified benefit plans	0	-92.9
Change In	'	'
Accounts receivable and accrued revenues	17	58.5
Inventories	13.2	33.8
Other current assets	36.9	42
Accounts payable	-49.3	-47.8
Accrued income taxes, net	24.4	28.8
Other current liabilities	17.1	-4.8
Other, net	43.4	-102.9
Cash Provided by Operating Activities	739.3	644.4
Investing Activities	'	'
Capital Expenditures	-363.6	-385.5
Investment in transmission affiliate	-6.9	-11.5
Change in restricted cash	2.7	36
Other, net	-37.8	-43
Cash Used in Investing Activities	-405.6	-404
Financing Activities	'	'
Dividends paid on common stock	-230	-134.7
Dividends paid on preferred stock	-0.9	-0.9
Issuance of long-term debt	250	0
Retirement of Long-term Debt	-300	0
Change in total short-term debt	-79.6	-105.4
Other, net	9.8	0
Cash Used in Financing Activities	-350.7	-241
Change in Cash and Cash Equivalents	-17	-0.6
Cash and Cash Equivalents at Beginning of Period	34.1	12.7
Cash and Cash Equivalents at End of Period	$17.10	$12.10

General_Information

General Information	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
General Information [Text Block]	'
	GENERAL INFORMATION
	Our accompanying unaudited consolidated condensed financial statements should be read in conjunction with Item 8, Financial Statements and Supplementary Data, in our 2012 Annual Report on Form 10-K. In the opinion of management, we have included all adjustments, normal and recurring in nature, necessary for a fair presentation of the results of operations, cash flows and financial position in the accompanying income statements, statements of cash flows and balance sheets. The results of operations for the three and nine months ended September 30, 2013 are not necessarily indicative of the results which may be expected for the entire fiscal year 2013 because of seasonal and other factors.

New_Accounting_Pronouncements

New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2013
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
New Accounting Pronouncements [Text Block]	'
	NEW ACCOUNTING PRONOUNCEMENTS
	Offsetting Assets and Liabilities: In December 2011, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) 2011-11, Disclosures about Offsetting Assets and Liabilities. The guidance requires enhanced disclosures about derivatives. Both gross and net information related to eligible transactions is required under the guidance. This guidance is effective for fiscal years and interim periods beginning on or after January 1, 2013, and must be applied retrospectively. We adopted this guidance on January 1, 2013, and applied it retrospectively. The adoption and retrospective application of this guidance did not have any material impact on our financial statements. See Note 6 -- Derivative Instruments for the enhanced disclosures.

Common_Equity

Common Equity	9 Months Ended
	Sep. 30, 2013
Stockholders' Equity Note [Abstract]	'
COMMON EQUITY	'
	COMMON EQUITY
	Stock Option Activity:   The following table identifies non-qualified stock options granted by the Compensation Committee of the Board of Directors (Compensation Committee):
		2013			2012
	Non-qualified stock options granted year to date	1,365,970			903,865
	Estimated fair value per non-qualified stock option	$	3.45		$	3.34
	Assumptions used to value the options using a binomial option pricing model:
	Risk-free interest rate	0.1% - 1.9%			0.1% - 2.0%
	Dividend yield	3.7		%	3.9		%
	Expected volatility	18		%	19		%
	Expected forfeiture rate	2		%	2		%
	Expected life (years)	5.9			5.9
	The risk-free interest rate is based on the U.S. Treasury interest rate whose term is consistent with the expected life of the stock options. Dividend yield, expected volatility, expected forfeiture rate and expected life assumptions are based on Wisconsin Energy's historical experience.
	The following is a summary of Wisconsin Energy stock option activity by our employees during the three and nine months ended September 30, 2013:
								Weighted-
								Average
					Weighted-			Remaining	Aggregate
			Number of		Average			Contractual Life	Intrinsic Value
	Stock Options		Options		Exercise Price			(Years)	(Millions)
	Outstanding as of July 1, 2013		8,056,421		$	26.62
	Granted		—		$	—
	Exercised		(78,806	)	$	21.41
	Forfeited		(4,680	)	$	35.36
	Outstanding as of September 30, 2013		7,972,935		$	26.66
	Outstanding as of January 1, 2013		8,416,876		$	23.96
	Granted		1,365,970		$	37.46
	Exercised		(1,799,881	)	$	22.19
	Forfeited		(10,030	)	$	35.37
	Outstanding as of September 30, 2013		7,972,935		$	26.66		5.5	$	109.4
	Exercisable as of September 30, 2013		5,683,535		$	23.03		4.2	$	98.6
	The intrinsic value of Wisconsin Energy options exercised by our employees was $1.7 million and $34.9 million for the three and nine months ended September 30, 2013 and $7.8 million and $38.7 million for the same periods in 2012, respectively. Cash received by Wisconsin Energy from exercises of its options by our employees was $39.9 million and $42.0 million for the nine months ended September 30, 2013 and 2012, respectively. The actual tax benefit realized for the tax deductions from option exercises for the same periods was $14.0 million and zero, respectively.
	The following table summarizes information about Wisconsin Energy stock options held by our employees and outstanding as of September 30, 2013:
			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)
	$16.72  to  $21.11		2,246,130		$	20.27		3.9	2,246,130		$	20.27	3.9
	$23.88  to  $29.35		3,539,460		$	24.65		4.5	3,246,200		$	24.23	4.2
	$34.87  to  $37.46		2,187,345		$	36.48		8.9	191,205		$	35.14	8.4
			7,972,935		$	26.66		5.5	5,683,535		$	23.03	4.2
	The following table summarizes information about our employees' non-vested Wisconsin Energy stock options during the three and nine months ended September 30, 2013:
					Weighted-Average
	Non-Vested Stock Options		Number of Options		Fair Value
	Non-vested as of July 1, 2013		2,294,780		$	3.38
	Granted		—		$	—
	Vested		(700	)	$	3.17
	Forfeited		(4,680	)	$	3.37
	Non-vested as of September 30, 2013		2,289,400		$	3.38
	Non-vested as of January 1, 2013		1,637,570		$	3.31
	Granted		1,365,970		$	3.45
	Vested		(704,110	)	$	3.33
	Forfeited		(10,030	)	$	3.37
	Non-vested as of September 30, 2013		2,289,400		$	3.38
	As of September 30, 2013, our total compensation costs related to non-vested Wisconsin Energy stock options held by our employees and not yet recognized was approximately $2.9 million, which is expected to be recognized over the next 20 months on a weighted-average basis.
	Restricted Shares:   The following restricted stock activity related to our employees occurred during the three and nine months ended September 30, 2013:
					Weighted-Average
	Restricted Shares		Number of Shares		Grant Date Fair Value
	Outstanding as of July 1, 2013		98,457
	Granted		—		$	—
	Released		—		$	—
	Forfeited		(231	)	$	34.48
	Outstanding as of September 30, 2013		98,226
	Outstanding as of January 1, 2013		126,392
Granted		53,055		$	37.71
Released		(67,722	)	$	26.77
Forfeited		(13,499	)	$	33.3
Outstanding as of September 30, 2013		98,226
Wisconsin Energy records the market value of the restricted stock awards on the date of grant and then we 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 zero and $2.8 million for the three and nine months ended September 30, 2013, and zero and $1.9 million for the same periods in 2012, respectively. The actual tax benefit realized for the tax deductions from released restricted shares was zero and $1.1 million for the three and nine months ended September 30, 2013, and zero for the same periods in 2012, respectively.
As of September 30, 2013, total compensation cost related to our share of Wisconsin Energy restricted stock not yet recognized was approximately $2.4 million, which is expected to be recognized over the next 22 months on a weighted-average basis.
Performance Units:   In January 2013 and 2012, the Compensation Committee awarded 230,245 and 333,685 Wisconsin Energy performance units, respectively, to our officers and other key employees under the Wisconsin Energy Performance Unit Plan. Performance units earned as of December 31, 2012 and 2011 vested and were settled during the first quarter of 2013 and 2012, and had a total intrinsic value of $17.1 million and $26.1 million, respectively. The actual tax benefit realized for the tax deductions from the settlement of performance units was approximately $6.2 million and $9.6 million, respectively. As of September 30, 2013, total compensation cost related to our share of Wisconsin Energy performance units not yet recognized was approximately $11.4 million, which is expected to be recognized over the next 20 months on a weighted-average basis.
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. See Note H -- Common Equity in our 2012 Annual Report on Form 10-K for additional information on these and other restrictions.
We do not believe that these restrictions will materially affect our operations or limit any dividend payments in the foreseeable future.

Long_Term_Debt

Long Term Debt	9 Months Ended
	Sep. 30, 2013
Long-term Debt and Capital Lease Obligations [Abstract]	'
Long-term Debt [Text Block]	'
	LONG-TERM DEBT
	In June 2013, we issued $250 million of 1.70% Debentures due June 15, 2018. The debentures were issued under an existing shelf registration statement filed with the SEC in February 2011. The net proceeds were used to repay short-term debt and for other corporate purposes.
	On May 15, 2013, we used short-term borrowings to retire $300 million of long-term debt that matured.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2013
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 Over-the-Counter (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 September 30, 2013
			Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Assets:
	Restricted Cash		$	—		$	—		$	—		$	—
	Derivatives		1.2			3.7			5.6			10.5
	Total		$	1.2		$	3.7		$	5.6		$	10.5
	Liabilities:
	Derivatives		$	1.1		$	0.1		$	—		$	1.2
	Total		$	1.1		$	0.1		$	—		$	1.2
	Recurring Fair Value Measures		As of December 31, 2012
			Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Assets:
	Restricted Cash		$	2.7		$	—		$	—		$	2.7
	Derivatives		1.2			11.5			4.7			17.4
	Total		$	3.9		$	11.5		$	4.7		$	20.1
	Liabilities:
	Derivatives		$	1.1		$	—		$	—		$	1.1
	Total		$	1.1		$	—		$	—		$	1.1
	We adopted ASU 2011-11, Disclosures about Offsetting Assets and Liabilities, on a retrospective basis. For additional information, see Note 2 -- New Accounting Pronouncements and Note 6 -- Derivative Instruments.
	Restricted cash consists of certificates of deposit and government backed interest bearing securities and represents the settlement we received from the United States Department of Energy (DOE) during the first quarter of 2011, which was returned, net of costs incurred, to customers. 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:
		Three Months Ended September 30						Nine Months Ended September 30
		2013			2012			2013			2012
		(Millions of Dollars)
	Beginning Balance	$	9.2		$	9.9		$	4.7		$	5.7
	Realized and unrealized gains (losses)	—			—			—			—
	Purchases	—			—			10.6			10.9
	Issuances	—			—			—			—
	Settlements	(3.6		)	(2.6		)	(9.7		)	(9.3		)
	Transfers in and/or out of Level 3	—			—			—			—
	Balance as of September 30	$	5.6		$	7.3		$	5.6		$	7.3
	Change in unrealized gains (losses) relating to instruments still held as of September 30	$	—		$	—		$	—		$	—
	Derivative instruments reflected in Level 3 of the hierarchy include MISO Financial Transmission Rights (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 6 -- 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 are as follows:
			September 30, 2013						December 31, 2012
	Financial Instruments		Carrying Amount			Fair			Carrying Amount			Fair
						Value						Value
			(Millions of Dollars)
	Preferred stock, no redemption required		$	30.4		$	26.3		$	30.4		$	26
	Long-term debt, including current portion		$	2,487.00		$	2,652.00		$	2,537.00		$	2,900.80
	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.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2013
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 Public Service Commission of Wisconsin (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 September 30, 2013, we recognized $2.5 million in regulatory assets and $9.8 million in regulatory liabilities related to derivatives in comparison to $3.7 million in regulatory assets and $16.7 million in regulatory liabilities as of December 31, 2012.
	We record our current derivative assets on the balance sheet in prepayments and other current assets and the current portion of the liabilities in other current liabilities. The long-term portion of our derivative assets of $0.7 million is recorded in other deferred charges and other assets as of September 30, 2013, and the long-term portion of our derivative liabilities of $0.2 million is recorded in other deferred credits and other liabilities as of September 30, 2013. Our Consolidated Condensed Balance Sheets as of September 30, 2013 and December 31, 2012 include:
			September 30, 2013								December 31, 2012
			Derivative Asset				Derivative Liability				Derivative Asset				Derivative Liability
			(Millions of Dollars)
	Natural Gas		$	1.2			$	1.2			$	1.2			$	1.1
	Fuel Oil		0.3				—				0.4				—
	FTRs		5.6				—				4.7				—
	Coal		3.4				—				11.1				—
	Total		$	10.5			$	1.2			$	17.4			$	1.1
	Our Consolidated Condensed 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) were as follows:
			Three Months Ended September 30, 2013						Three Months Ended September 30, 2012
			Volume		Gains (Losses)				Volume		Gains (Losses)
					(Millions of Dollars)						(Millions of Dollars)
	Natural Gas		3.6 million Dth		$	(0.5	)		9.4 million Dth		$	(2.5	)
	Fuel Oil		2.5 million gallons		(0.1		)		1.7 million gallons		0.1
	FTRs		6,322 MW		5.4				5,927 MW		2.9
	Total				$	4.8					$	0.5
			Nine Months Ended September 30, 2013						Nine Months Ended September 30, 2012
			Volume		Gains (Losses)				Volume		Gains (Losses)
					(Millions of Dollars)						(Millions of Dollars)
	Natural Gas		18.2 million Dth		$	(2.6	)		27.4 million Dth		$	(16.9	)
	Fuel Oil		6.2 million gallons		0.1				5.5 million gallons		1.5
	FTRs		17,410 MW		11				16,581 MW		5.1
	Total				$	8.5					$	(10.3	)
	As of September 30, 2013 and December 31, 2012, we posted collateral of $1.9 million and $2.1 million, 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 September 30, 2013 and December 31, 2012.
		September 30, 2013								December 31, 2012
		Derivative				Derivative				Derivative				Derivative
		Asset				Liability				Asset				Liability
		(Millions of Dollars)
	Gross Amount Recognized on the Balance Sheet	$	10.5			$	1.2			$	17.4			$	1.1
	Gross Amount Not Offset on Balance Sheet (a)	(0.3		)		(1.0		)		(0.4		)		(1.1		)
	Net Amount	$	10.2			$	0.2			$	17			$	—
	(a)	Gross Amount Not Offset on Balance Sheet includes cash collateral posted of $0.8 million and $0.6 million as of September 30, 2013 and December 31, 2012, respectively.

Benefits

Benefits	9 Months Ended
	Sep. 30, 2013
General Discussion of Pension and Other Postretirement Benefits [Abstract]	'
BENEFITS	'
	BENEFITS
	The components of our net periodic pension and Other Post-Retirement Employee Benefits (OPEB) costs for the three and nine months ended September 30 were as follows:
		Pension Costs
		Three Months Ended September 30						Nine Months Ended September 30
	Benefit Plan Cost Components	2013			2012			2013			2012
		(Millions of Dollars)
	Net Periodic Benefit Cost
	Service cost	$	3.5		$	4.9		$	10.4		$	14.8
	Interest cost	13.1			14.2			39.3			42.6
	Expected return on plan assets	(19.3		)	(17.9		)	(57.9		)	(53.8		)
	Amortization of:
	Prior service cost	0.5			0.5			1.6			1.6
	Actuarial loss	10.4			7.6			31.3			22.6
	Net Periodic Benefit Cost	$	8.2		$	9.3		$	24.7		$	27.8
		OPEB Costs
		Three Months Ended September 30						Nine Months Ended September 30
	Benefit Plan Cost Components	2013			2012			2013			2012
		(Millions of Dollars)
	Net Periodic Benefit Cost
	Service cost	$	2.4		$	2.5		$	7.1		$	7.4
	Interest cost	3.2			4.2			9.5			12.6
	Expected return on plan assets	(3.7		)	(3.3		)	(10.9		)	(9.8		)
	Amortization of:
	Transition obligation	—			—			—			0.2
	Prior service (credit)	(0.5		)	(0.5		)	(1.4		)	(1.4		)
	Actuarial loss	0.4			1.3			1.1			3.7
	Net Periodic Benefit Cost	$	1.8		$	4.2		$	5.4		$	12.7
	During the first nine months of 2013 and 2012, we contributed zero and $92.9 million, respectively, to our qualified benefit plans. Future contributions to the plans will be dependent upon many factors, including the performance of existing plan assets and long-term discount rates.
	Postemployment Benefits:   Postemployment benefits provided to former or inactive employees are recognized when an event occurs. The estimated liability for such benefits was $2.4 million as of September 30, 2013 and December 31, 2012.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
Segment Information [Abstract]	'
Segment Information [Text Block]	'
	SEGMENT INFORMATION
	Summarized financial information concerning our reportable segments for the three and nine months ended September 30, 2013 and 2012 is shown in the following table:
			Reportable Segments
			Electric		Gas			Steam			Total
			(Millions of Dollars)
	Three Months Ended
	September 30, 2013
	Operating Revenues (a)		$	911	$	48		$	5.6		$	964.6
	Operating Income (Loss)		$	168.6	$	(1.7	)	$	(2.3	)	$	164.6
	September 30, 2012
	Operating Revenues (a)		$	901.2	$	45.4		$	5.3		$	951.9
	Operating Income (Loss)		$	193.9	$	1.9		$	(2.5	)	$	193.3
	Nine Months Ended
	September 30, 2013
	Operating Revenues (a)		$	2,516.50	$	304.6		$	28.6		$	2,849.70
	Operating Income		$	415.4	$	44.6		$	1.9		$	461.9
	September 30, 2012
	Operating Revenues (a)		$	2,451.10	$	263.3		$	24.7		$	2,739.10
	Operating Income (Loss)		$	470.1	$	30.2		$	(2.4	)	$	497.9
	(a)	We account for all intersegment revenues at rates established by the PSCW. Intersegment revenues were not material.

Variable_Interest_Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2013
Variable Interest Entities [Abstract]	'
Variable Interest Entities Disclosure [Text Block]	'
	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 nine 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 $226.0 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 for the nine months ended September 30, 2013 and 2012 were $37.8 million and $44.5 million, respectively. Our maximum exposure to loss is limited to the capacity payments under the contracts.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies [Text Block]	'
	COMMITMENTS AND CONTINGENCIES
	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 Wisconsin Department of Natural Resources (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 $18 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 September 30, 2013, we have established reserves of $7.2 million 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.
	Divested Assets:   Pursuant to the sale of the Point Beach Nuclear Power Plant, we agreed to indemnification provisions customary to transactions involving the sale of nuclear assets. We also provided customary indemnifications to Wisconsin Power and Light Company, a subsidiary of Alliant Energy Corp. in connection with the sale of our interest in Edgewater Generating Unit 5.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2013
Supplemental Cash Flow Information [Abstract]	'
Supplemental Cash Flow Information	'
	SUPPLEMENTAL CASH FLOW INFORMATION
	During the nine months ended September 30, 2013, we paid $66.6 million in interest, net of amounts capitalized, and received $35.0 million in net refunds from income taxes. During the nine months ended September 30, 2012, we paid $54.1 million in interest, net of amounts capitalized, and paid $14.7 million in income taxes, net of refunds.
	As of September 30, 2013 and 2012, the amount of accounts payable related to capital expenditures was $3.3 million and $25.3 million, respectively.
	During the nine months ended September 30, 2013 and 2012, our equity in earnings from ATC was $44.9 million and $43.0 million, respectively. During the nine months ended September 30, 2013 and 2012, distributions received from ATC were $35.5 million and $34.3 million, respectively.

Common_Equity_Tables

Common Equity (Tables)	9 Months Ended
	Sep. 30, 2013
Stockholders' Equity Note [Abstract]	'
Assumptions for valuing options using binomial option pricing model	'
		2013			2012
	Non-qualified stock options granted year to date	1,365,970			903,865
	Estimated fair value per non-qualified stock option	$	3.45		$	3.34
	Assumptions used to value the options using a binomial option pricing model:
	Risk-free interest rate	0.1% - 1.9%			0.1% - 2.0%
	Dividend yield	3.7		%	3.9		%
	Expected volatility	18		%	19		%
	Expected forfeiture rate	2		%	2		%
	Expected life (years)	5.9			5.9
Stock option activity	'
								Weighted-
								Average
					Weighted-			Remaining	Aggregate
			Number of		Average			Contractual Life	Intrinsic Value
	Stock Options		Options		Exercise Price			(Years)	(Millions)
	Outstanding as of July 1, 2013		8,056,421		$	26.62
	Granted		—		$	—
	Exercised		(78,806	)	$	21.41
	Forfeited		(4,680	)	$	35.36
	Outstanding as of September 30, 2013		7,972,935		$	26.66
	Outstanding as of January 1, 2013		8,416,876		$	23.96
	Granted		1,365,970		$	37.46
	Exercised		(1,799,881	)	$	22.19
	Forfeited		(10,030	)	$	35.37
	Outstanding as of September 30, 2013		7,972,935		$	26.66		5.5	$	109.4
	Exercisable as of September 30, 2013		5,683,535		$	23.03		4.2	$	98.6
Stock options outstanding	'
			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)
	$16.72  to  $21.11		2,246,130		$	20.27		3.9	2,246,130		$	20.27	3.9
	$23.88  to  $29.35		3,539,460		$	24.65		4.5	3,246,200		$	24.23	4.2
	$34.87  to  $37.46		2,187,345		$	36.48		8.9	191,205		$	35.14	8.4
			7,972,935		$	26.66		5.5	5,683,535		$	23.03	4.2
Non-vested options	'
					Weighted-Average
	Non-Vested Stock Options		Number of Options		Fair Value
	Non-vested as of July 1, 2013		2,294,780		$	3.38
	Granted		—		$	—
	Vested		(700	)	$	3.17
	Forfeited		(4,680	)	$	3.37
	Non-vested as of September 30, 2013		2,289,400		$	3.38
	Non-vested as of January 1, 2013		1,637,570		$	3.31
	Granted		1,365,970		$	3.45
	Vested		(704,110	)	$	3.33
	Forfeited		(10,030	)	$	3.37
	Non-vested as of September 30, 2013		2,289,400		$	3.38
Restricted stock activity	'
					Weighted-Average
	Restricted Shares		Number of Shares		Grant Date Fair Value
	Outstanding as of July 1, 2013		98,457
	Granted		—		$	—
	Released		—		$	—
	Forfeited		(231	)	$	34.48
	Outstanding as of September 30, 2013		98,226
	Outstanding as of January 1, 2013		126,392
	Granted		53,055		$	37.71
	Released		(67,722	)	$	26.77
	Forfeited		(13,499	)	$	33.3
	Outstanding as of September 30, 2013		98,226

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value Measurements (Tables) [Abstract]	'
Financial assets and liabilities by level within the fair value hierarchy	'
	Recurring Fair Value Measures		As of September 30, 2013
			Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Assets:
	Restricted Cash		$	—		$	—		$	—		$	—
	Derivatives		1.2			3.7			5.6			10.5
	Total		$	1.2		$	3.7		$	5.6		$	10.5
	Liabilities:
	Derivatives		$	1.1		$	0.1		$	—		$	1.2
	Total		$	1.1		$	0.1		$	—		$	1.2
	Recurring Fair Value Measures		As of December 31, 2012
			Level 1			Level 2			Level 3			Total
			(Millions of Dollars)
	Assets:
	Restricted Cash		$	2.7		$	—		$	—		$	2.7
	Derivatives		1.2			11.5			4.7			17.4
	Total		$	3.9		$	11.5		$	4.7		$	20.1
	Liabilities:
	Derivatives		$	1.1		$	—		$	—		$	1.1
	Total		$	1.1		$	—		$	—		$	1.1
Fair value of derivatives classified as Level 3 in the fair value hierarchy	'
		Three Months Ended September 30						Nine Months Ended September 30
		2013			2012			2013			2012
		(Millions of Dollars)
	Beginning Balance	$	9.2		$	9.9		$	4.7		$	5.7
	Realized and unrealized gains (losses)	—			—			—			—
	Purchases	—			—			10.6			10.9
	Issuances	—			—			—			—
	Settlements	(3.6		)	(2.6		)	(9.7		)	(9.3		)
	Transfers in and/or out of Level 3	—			—			—			—
	Balance as of September 30	$	5.6		$	7.3		$	5.6		$	7.3
	Change in unrealized gains (losses) relating to instruments still held as of September 30	$	—		$	—		$	—		$	—
Carrying amount and estimated fair value of certain financial instruments	'
			September 30, 2013						December 31, 2012
	Financial Instruments		Carrying Amount			Fair			Carrying Amount			Fair
						Value						Value
			(Millions of Dollars)
	Preferred stock, no redemption required		$	30.4		$	26.3		$	30.4		$	26
	Long-term debt, including current portion		$	2,487.00		$	2,652.00		$	2,537.00		$	2,900.80

Derivative_Instruments_Tables

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Derivative Instruments (Tables) [Abstract]	'
Derivative instruments in balance sheet	'
			September 30, 2013								December 31, 2012
			Derivative Asset				Derivative Liability				Derivative Asset				Derivative Liability
			(Millions of Dollars)
	Natural Gas		$	1.2			$	1.2			$	1.2			$	1.1
	Fuel Oil		0.3				—				0.4				—
	FTRs		5.6				—				4.7				—
	Coal		3.4				—				11.1				—
	Total		$	10.5			$	1.2			$	17.4			$	1.1
Derivative instruments' estimated notional volumes and gain (losses)	'
			Three Months Ended September 30, 2013						Three Months Ended September 30, 2012
			Volume		Gains (Losses)				Volume		Gains (Losses)
					(Millions of Dollars)						(Millions of Dollars)
	Natural Gas		3.6 million Dth		$	(0.5	)		9.4 million Dth		$	(2.5	)
	Fuel Oil		2.5 million gallons		(0.1		)		1.7 million gallons		0.1
	FTRs		6,322 MW		5.4				5,927 MW		2.9
	Total				$	4.8					$	0.5
			Nine Months Ended September 30, 2013						Nine Months Ended September 30, 2012
			Volume		Gains (Losses)				Volume		Gains (Losses)
					(Millions of Dollars)						(Millions of Dollars)
	Natural Gas		18.2 million Dth		$	(2.6	)		27.4 million Dth		$	(16.9	)
	Fuel Oil		6.2 million gallons		0.1				5.5 million gallons		1.5
	FTRs		17,410 MW		11				16,581 MW		5.1
	Total				$	8.5					$	(10.3	)
Offsetting Assets and Liabilities [Table Text Block]	'
		September 30, 2013								December 31, 2012
		Derivative				Derivative				Derivative				Derivative
		Asset				Liability				Asset				Liability
		(Millions of Dollars)
	Gross Amount Recognized on the Balance Sheet	$	10.5			$	1.2			$	17.4			$	1.1
	Gross Amount Not Offset on Balance Sheet (a)	(0.3		)		(1.0		)		(0.4		)		(1.1		)
	Net Amount	$	10.2			$	0.2			$	17			$	—
	(a)	Gross Amount Not Offset on Balance Sheet includes cash collateral posted of $0.8 million and $0.6 million as of September 30, 2013 and December 31, 2012, respectively.

Benefits_Tables

Benefits (Tables)	9 Months Ended
	Sep. 30, 2013
Benefits (Tables) [Abstract]	'
Components of net periodic pension and OPEB costs	'
		Pension Costs
		Three Months Ended September 30						Nine Months Ended September 30
	Benefit Plan Cost Components	2013			2012			2013			2012
		(Millions of Dollars)
	Net Periodic Benefit Cost
	Service cost	$	3.5		$	4.9		$	10.4		$	14.8
	Interest cost	13.1			14.2			39.3			42.6
	Expected return on plan assets	(19.3		)	(17.9		)	(57.9		)	(53.8		)
	Amortization of:
	Prior service cost	0.5			0.5			1.6			1.6
	Actuarial loss	10.4			7.6			31.3			22.6
	Net Periodic Benefit Cost	$	8.2		$	9.3		$	24.7		$	27.8
		OPEB Costs
		Three Months Ended September 30						Nine Months Ended September 30
	Benefit Plan Cost Components	2013			2012			2013			2012
		(Millions of Dollars)
	Net Periodic Benefit Cost
	Service cost	$	2.4		$	2.5		$	7.1		$	7.4
	Interest cost	3.2			4.2			9.5			12.6
	Expected return on plan assets	(3.7		)	(3.3		)	(10.9		)	(9.8		)
	Amortization of:
	Transition obligation	—			—			—			0.2
	Prior service (credit)	(0.5		)	(0.5		)	(1.4		)	(1.4		)
	Actuarial loss	0.4			1.3			1.1			3.7
	Net Periodic Benefit Cost	$	1.8		$	4.2		$	5.4		$	12.7

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting Information [Line Items]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
			Reportable Segments
			Electric		Gas			Steam			Total
			(Millions of Dollars)
	Three Months Ended
	September 30, 2013
	Operating Revenues (a)		$	911	$	48		$	5.6		$	964.6
	Operating Income (Loss)		$	168.6	$	(1.7	)	$	(2.3	)	$	164.6
	September 30, 2012
	Operating Revenues (a)		$	901.2	$	45.4		$	5.3		$	951.9
	Operating Income (Loss)		$	193.9	$	1.9		$	(2.5	)	$	193.3
	Nine Months Ended
	September 30, 2013
	Operating Revenues (a)		$	2,516.50	$	304.6		$	28.6		$	2,849.70
	Operating Income		$	415.4	$	44.6		$	1.9		$	461.9
	September 30, 2012
	Operating Revenues (a)		$	2,451.10	$	263.3		$	24.7		$	2,739.10
	Operating Income (Loss)		$	470.1	$	30.2		$	(2.4	)	$	497.9
	(a)	We account for all intersegment revenues at rates established by the PSCW. Intersegment revenues were not material.

Common_Equity_Details

Common Equity (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Performance units [Member]	'	'	'	'
Common Equity (Textuals) [Abstract]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	'	'	230,245	333,685
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	'	'	$17.10	$26.10
Tax Benefit from Stock Options Exercised	'	'	6.2	9.6
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	11.4	'	11.4	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'	'	'20 months	'
Restricted stock [Member]	'	'	'	'
Common Equity (Textuals) [Abstract]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0	'	53,055	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	0	0	2.8	1.9
Tax Benefit from Stock Options Exercised	'	'	'	0
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$2.40	'	$2.40	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'	'	'22 months	'

Common_Equity_1_Details

Common Equity 1 (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	'	3.70%	3.90%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	'	18.00%	19.00%
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Forfeiture Rate	'	2.00%	2.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	'	'5 years 11 months	'5 years 11 months
Stock options [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	0	1,365,970	903,865
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	'	$3.45	$3.34
Lower Range [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	'	0.10%	0.10%
Upper Range [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	'	1.90%	2.00%

Common_Equity_2_Details

Common Equity 2 (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013
					Stock options [Member]	Stock options [Member]	Stock options [Member]	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, Outstanding, Number	'	'	'	'	'	8,416,876	'	8,056,421
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period	'	'	'	'	0	1,365,970	903,865	'
Share Based Compensation Arrangement By Share Based Payment Award Options Grant In Period Weighted Average Exercise Price	'	'	'	'	$0	$37.46	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	'	'	'	'	-78,806	-1,799,881	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	'	'	'	'	-4,680	-10,030	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	7,972,935	'	7,972,935	'	7,972,935	7,972,935	'	8,056,421
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	'	'	'	'	'	$23.96	'	$26.62
Share Based Compensation Arrangement By Share Based Payment Awards Options Exercises In Period Weighted Average Exercise Price	'	'	'	'	$21.41	$22.19	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	'	'	'	'	$35.36	$35.37	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$26.66	'	$26.66	'	$26.66	$26.66	'	$26.62
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Outstanding Options Weighted Average Remaining Contractual Period	'	'	'	'	'	'5 years 6 months	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	'	'	'	'	$109.40	$109.40	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	5,683,535	'	5,683,535	'	5,683,535	5,683,535	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$23.03	'	$23.03	'	$23.03	$23.03	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term	'	'	'4 years 2 months	'	'	'4 years 2 months	'	'
Share Based Compensation Arrangement by Share Based Payments Award, Options Exercisable, Intrinsic Value	'	'	'	'	98.6	98.6	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	1.7	7.8	34.9	38.7	'	'	'	'
Proceeds from Stock Options Exercised	'	'	39.9	42	'	'	'	'
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	'	'	$14	$0	'	'	'	'

Common_Equity_3_Details

Common Equity 3 (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	7,972,935
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$26.66
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	'5 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	5,683,535
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$23.03
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term	'4 years 2 months
Exercise Price, Range One [Member]	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	2,246,130
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$20.27
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	'3 years 11 months
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options	2,246,130
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$20.27
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term	'3 years 11 months
Exercise Price, Range One [Member] | Minimum [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, Outstanding, Weighted Average Exercise Price	$16.72
Exercise Price, Range One [Member] | Maximum [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, Outstanding, Weighted Average Exercise Price	$21.11
Exercise Price, Range Two [Member]	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	3,539,460
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$24.65
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	'4 years 6 months
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options	3,246,200
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$24.23
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term	'4 years 2 months
Exercise Price, Range Two [Member] | Minimum [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, Outstanding, Weighted Average Exercise Price	$23.88
Exercise Price, Range Two [Member] | Maximum [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, Outstanding, Weighted Average Exercise Price	$29.35
Exercise Price, Range Three [Member]	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options	2,187,345
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$36.48
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	'8 years 11 months
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options	191,205
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$35.14
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term	'8 years 5 months
Exercise Price, Range Three [Member] | Minimum [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, Outstanding, Weighted Average Exercise Price	$34.87
Exercise Price, Range Three [Member] | Maximum [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, Outstanding, Weighted Average Exercise Price	$37.46

Common_Equity_4_Details

Common Equity 4 (Details) (USD $)	3 Months Ended	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013	Mar. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	7,972,935	7,972,935	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$26.66	$26.66	'
Performance units [Member]	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'	'	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'	'20 months	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$11.40	$11.40	'
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, Options, Outstanding, Number	'	1,637,570	2,294,780
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period	0	1,365,970	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period	-700	-704,110	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	-4,680	-10,030	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	2,289,400	2,289,400	2,294,780
Non-vested options outstanding beginning balance, weighted average fair value	'	$3.31	$3.38
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$0	$3.45	'
Share Based Compensation Arrangements By Share Based Payment Awards Options Vested In Period Weighted Average Fair Value	$3.17	$3.33	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Intrinsic Value	($3.37)	($3.37)	'
Non-vested options outstanding ending balance, weighted average fair value	'	'	$3.38
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$3.38	$3.38	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'	'20 months	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$2.90	$2.90	'

Common_Equity_5_Details

Common Equity 5 (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	'	'	$14	$0	'
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	'	'	'3 years	'	'
Share Based Compensation Arrangement By Share Based Payment Award Award Percentage To Vest Each Year After Grant Date	'	'	33.00%	'	'
Restricted stock [Member]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	0	0	2.8	1.9	'
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	0	0	1.1	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	'	'	126,392	'	98,457
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0	'	53,055	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	0	'	-67,722	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	-231	'	-13,499	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	98,226	'	98,226	'	98,457
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$0	'	$37.71	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$0	'	$26.77	'	'
Share Based Compensation Arrangement By Share Based Payment Awards Equity Instruments Other Than Options Forfeited In Period Weighted Average Grant Date Fair Value	$34.48	'	$33.30	'	'
Tax Benefit from Stock Options Exercised	'	'	'	0	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	2.4	'	2.4	'	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'	'	'22 months	'	'
Performance units [Member]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	'	'	17.1	26.1	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	'	'	230,245	333,685	'
Tax Benefit from Stock Options Exercised	'	'	6.2	9.6	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$11.40	'	$11.40	'	'
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	'	'	'20 months	'	'

Long_Term_Debt_Details

Long Term Debt (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Wis Elec Debenture due June, 15 2018 [Domain]	'
Long Term Debt [Line Items]	'
Issuance of long-term debt	$250
Interest rate on long-term debt	1.70%
Wis Elec Debentures due May 15 2013 [Domain]	'
Long Term Debt [Line Items]	'
Retirement of long-term Debt	$300

Fair_Value_Measurements_Assets

Fair Value Measurements Assets and Liabilities (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]	'	'
Restricted Cash	$0	$2.70
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	1.2	1.2
Fair Value Assets Measured on Recurring Basis Total Assets	1.2	3.9
Fair Value, Liabilities Measured on Recurring Basis, Derivative Financial Instruments, Liabilities	1.1	1.1
Fair Value Liabilities Measured on Recurring Basis Total Liabilities	1.1	1.1
Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]	'	'
Restricted Cash	0	0
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	3.7	11.5
Fair Value Assets Measured on Recurring Basis Total Assets	3.7	11.5
Fair Value, Liabilities Measured on Recurring Basis, Derivative Financial Instruments, Liabilities	0.1	0
Fair Value Liabilities Measured on Recurring Basis Total Liabilities	0.1	0
Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]	'	'
Restricted Cash	0	0
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	5.6	4.7
Fair Value Assets Measured on Recurring Basis Total Assets	5.6	4.7
Fair Value, Liabilities Measured on Recurring Basis, Derivative Financial Instruments, Liabilities	0	0
Fair Value Liabilities Measured on Recurring Basis Total Liabilities	0	0
Estimate of Fair Value, Fair Value Disclosure [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]	'	'
Restricted Cash	0	2.7
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	10.5	17.4
Fair Value Assets Measured on Recurring Basis Total Assets	10.5	20.1
Fair Value, Liabilities Measured on Recurring Basis, Derivative Financial Instruments, Liabilities	1.2	1.1
Fair Value Liabilities Measured on Recurring Basis Total Liabilities	$1.20	$1.10

Fair_Value_Measurements_Deriva

Fair Value Measurements, Derivatives (Details) (Derivative [Member], USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Member]	'	'	'	'
Fair value of derivatives classified as Level 3 in the fair value hierarchy	'	'	'	'
Beginning Balance	$9.20	$9.90	$4.70	$5.70
Realized and unrealized gains (losses)	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	10.6	10.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	-3.6	-2.6	-9.7	-9.3
Transfers in and/or out of Level 3	0	0	0	0
Ending Balance	5.6	7.3	5.6	7.3
Change in unrealized gains (losses) relating to instruments still held as of period end	$0	$0	$0	$0

Fair_Value_Measurements_Financ

Fair Value Measurements, Financial Instruments (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Financial Instruments	'	'
Preferred stock	$30.40	$30.40
Carrying (Reported) Amount, Fair Value Disclosure [Member]	'	'
Financial Instruments	'	'
Preferred stock	30.4	30.4
Long-term debt including current portion	2,487	2,537
Estimate of Fair Value, Fair Value Disclosure [Member]	'	'
Financial Instruments	'	'
Preferred stock	26.3	26
Long-term debt including current portion	$2,652	$2,900.80

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Derivative asset	$10.50	'	$10.50	'	$17.40
Derivative liability	1.2	'	1.2	'	1.1
Gains (losses)	4.8	0.5	8.5	-10.3	'
Derivative Instruments (Textuals)	'	'	'	'	'
Collateral in margin accounts	1.9	'	1.9	'	2.1
Other Deferred Charges and Other Assets [Member]	'	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Long-term portion of derivative assets	0.7	'	0.7	'	'
Other Deferred Credits and Other Liabilities [Member]	'	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Long-term portion of derivative liabilities	0.2	'	0.2	'	'
Natural Gas [Member]	'	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Derivative asset	1.2	'	1.2	'	1.2
Derivative liability	1.2	'	1.2	'	1.1
Volume of derivative instruments	'3.6 million Dth	'9.4 million Dth	'18.2 million Dth	'27.4 million Dth	'
Gains (losses)	-0.5	-2.5	-2.6	-16.9	'
Fuel Oil [Member]	'	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Derivative asset	0.3	'	0.3	'	0.4
Derivative liability	0	'	0	'	0
Volume of derivative instruments	'2.5 million gallons	'1.7 million gallons	'6.2 million gallons	'5.5 million gallons	'
Gains (losses)	-0.1	0.1	0.1	1.5	'
Ftrs [Member]	'	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Derivative asset	5.6	'	5.6	'	4.7
Derivative liability	0	'	0	'	0
Volume of derivative instruments	'6,322 MW	'5,927 MW	'17,410 MW	'16,581 MW	'
Gains (losses)	5.4	2.9	11	5.1	'
Coal [Member]	'	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'	'
Derivative asset	3.4	'	3.4	'	11.1
Derivative liability	$0	'	$0	'	$0

Derivative_Instruments_Details1

Derivative Instruments (Details 1) (Derivative [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Derivative [Member]	'	'
Regulatory Assets [Line Items]	'	'
Regulatory assets related to derivatives	$2.50	$3.70

Derivative_Instruments_Details2

Derivative Instruments (Details 2) (Derivative [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Derivative [Member]	'	'
Regulatory Liabilities [Line Items]	'	'
Regulatory liabilities related to derivatives	$9.80	$16.70

Derivative_Instruments_Derivat

Derivative Instruments Derivative Instruments (Details 3) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Derivative [Line Items]	'	'
Collateral Already Posted, Aggregate Fair Value	$1.90	$2.10
Derviative Instrument by Counterparty, Gross Amount Recognized on Balance Sheet [Member]	'	'
Derivative [Line Items]	'	'
Derivative Assets	10.5	17.4
Derivative Liabilities	1.2	1.1
Derviative Instrument by Counterparty, Gross Amount Not Offset on Balance Sheet [Member] [Member]	'	'
Derivative [Line Items]	'	'
Collateral Already Posted, Aggregate Fair Value	0.8	0.6
Derivative Assets	-0.3	-0.4
Derivative Liabilities	-1	-1.1
Derviative Instrument by Counterparty, Net Amount [Member]	'	'
Derivative [Line Items]	'	'
Derivative Assets	10.2	17
Derivative Liabilities	$0.20	$0

Benefits_Details

Benefits (Details) (USD $)	9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
				Pension Plans, Defined Benefit [Member]	Pension Plans, Defined Benefit [Member]	Pension Plans, Defined Benefit [Member]	Pension Plans, Defined Benefit [Member]	Other Postretirement Benefit Plans, Defined Benefit [Member]	Other Postretirement Benefit Plans, Defined Benefit [Member]	Other Postretirement Benefit Plans, Defined Benefit [Member]	Other Postretirement Benefit Plans, Defined Benefit [Member]
Net Periodic Benefit Cost	'	'	'	'	'	'	'	'	'	'	'
Service cost	'	'	'	$3.50	$4.90	$10.40	$14.80	$2.40	$2.50	$7.10	$7.40
Interest cost	'	'	'	13.1	14.2	39.3	42.6	3.2	4.2	9.5	12.6
Expected return on plan assets	'	'	'	-19.3	-17.9	-57.9	-53.8	-3.7	-3.3	-10.9	-9.8
Amortization of:	'	'	'	'	'	'	'	'	'	'	'
Transition obligation	'	'	'	'	'	'	'	0	0	0	0.2
Prior service cost (credit)	'	'	'	0.5	0.5	1.6	1.6	-0.5	-0.5	-1.4	-1.4
Actuarial loss	'	'	'	10.4	7.6	31.3	22.6	0.4	1.3	1.1	3.7
Net Periodic Benefit Cost	'	'	'	8.2	9.3	24.7	27.8	1.8	4.2	5.4	12.7
Benefits (Textuals) [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Pension and Other Postretirement Benefit Contributions	0	92.9	'	'	'	'	'	'	'	'	'
Estimated liability of Postemployment benefits	$2.40	'	$2.40	'	'	'	'	'	'	'	'

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]	'		'		'		'
Operating Revenues	$964.60	[1]	$951.90	[1]	$2,849.70	[1]	$2,739.10	[1]
Operating Income (Loss)	164.6		193.3		461.9		497.9
Reportable Operating Segment Electric [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating Revenues	911	[1]	901.2	[1]	2,516.50	[1]	2,451.10	[1]
Operating Income (Loss)	168.6		193.9		415.4		470.1
Reportable Operating Segment Gas [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating Revenues	48	[1]	45.4	[1]	304.6	[1]	263.3	[1]
Operating Income (Loss)	-1.7		1.9		44.6		30.2
Reportable Operating Segment Steam [Member]	'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'
Operating Revenues	5.6	[1]	5.3	[1]	28.6	[1]	24.7	[1]
Operating Income (Loss)	($2.30)		($2.50)		$1.90		($2.40)
[1]	We account for all intersegment revenues at rates established by the PSCW. Intersegment revenues were not material.

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Variable Interest Entity [Line Items]	'	'
Power capacity under capital lease (MW)	236	'
Capital Lease Agreement With Vie Remaining Term In Years	9	'
Total payments over remaining terms of the agreement	$226	'
Total capacity and lease payments	$37.80	$44.50

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (Manufactured Gas Plant Sites [Member], USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Manufactured Gas Plant Sites [Member]	'
Commitments and Contingencies [Line Items]	'
Loss Contingency, Range of Possible Loss, Minimum	$6
Loss Contingency, Range of Possible Loss, Maximum	18
Period for future costs of detailed site investigation and remediation costs	'over the next ten years
Accrual for Environmental Loss Contingencies, Provision for New Losses	$7.20

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Supplemental Cash Flow Information (Textuals)	'	'	'	'
Interest paid, net of amounts capitalized	'	'	$66.60	$54.10
Net refunds from income taxes	'	'	35	'
Income taxes paid, net of refunds	'	'	'	14.7
Accounts payable related to capital expenditures	3.3	25.3	3.3	25.3
Income (Loss) from Equity Method Investments	15.1	15	44.9	43
Distributions from transmission affiliate	'	'	$35.50	$34.30