COMMON EQUITY (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Dividend Payment Restrictions
Total restricted net assets	1,676.0
Equity in undistributed earnings of 50% or less owned investees accounted under equity method investments	129.4
Maximum
Dividend Payment Restrictions
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
Cumulative period of interest payment deferral on Junior Subordinated Notes	10 years
Minimum
Dividend Payment Restrictions
Number of periods which can be deferred on Junior Subordinated Notes	1
WPS \| Maximum
Dividend Payment Restrictions
Percentage of previous period's dividend as restriction on current period dividends	103.00%
Percentage of common stockholders equity to total capitalization for dividend payment restrictions	25.00%
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
WPS \| Minimum
Dividend Payment Restrictions
Common equity ratio required to be maintained (as a percent)	51.00%
PGL \| Maximum
Dividend Payment Restrictions
Debt to capitalization ratio required to be maintained (as a percent)	65.00%

Represents the common equity ratio which is required to be maintained.

No definition available.

Name:	teg_CommonEquityRatioToBeMaintained
Namespace Prefix:	teg_
Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Represents the number of periods for which interest payments on junior subordinated notes, can be deferred.

+ References

No definition available.

+ Details

Name:	teg_DebtInstrumentInterestPaymentDeferralOptionNumberOfPeriods
Namespace Prefix:	teg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of years for which interest payments, on junior subordinated notes, of particular period can be deferred.

+ References

No definition available.

+ Details

Name:	teg_DebtInstrumentInterestPaymentDeferralPeriod
Namespace Prefix:	teg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents debt to capitalization ratio required to be maintained.

+ References

No definition available.

+ Details

Name:	teg_DividendPaymentRestrictionsDebtToCapitalizationRatio
Namespace Prefix:	teg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	teg_DividendPaymentRestrictionsLineItems
Namespace Prefix:	teg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of common stockholders equity to total capitalization for dividend payment restrictions.

+ References

No definition available.

+ Details

Name:	teg_DividendPaymentRestrictionsPercentageOfCommonStockholdersEquityToTotalCapitalization
Namespace Prefix:	teg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of previous period's dividend as restriction on current period's dividends.

+ References

No definition available.

+ Details

Name:	teg_PercentageOfPreviousPeriodDividendAsRestrictionOnCurrentPeriodDividends
Namespace Prefix:	teg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of restricted net assets of consolidated and unconsolidated subsidiaries as of the end of the most recently completed fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(e)(3)(ii))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph e

-Subparagraph 3

-Article 4

+ Details

Name:	us-gaap_AmountOfRestrictedNetAssetsForConsolidatedAndUnconsolidatedSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of consolidated retained earnings that represent undistributed (not yet received) earnings from 50% or less owned persons accounted for by the equity method (equity method investees).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 852

-SubTopic 20

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6462270&loc=d3e57205-112772

+ Details

Name:	us-gaap_RetainedEarningsUndistributedEarningsFromEquityMethodInvestees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant