COMMON EQUITY (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Dividend Payment Restrictions
Total restricted net assets	$ 1,848.7
Equity in undistributed earnings of 50% or less owned investees accounted for by the equity method	$ 143.1
Maximum
Dividend Payment Restrictions
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
Equity method investment, ownership interest (as a percent)	50.00%
Cumulative period of interest payment deferral on Junior Subordinated Notes	10 years
Minimum
Dividend Payment Restrictions
Number of periods for which interest payments can be deferred on Junior Subordinated Notes	1
PGL \| Maximum
Dividend Payment Restrictions
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
WPS \| Maximum
Dividend Payment Restrictions
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 \| Maximum \| Public Service Commission of Wisconsin (PSCW)
Dividend Payment Restrictions
Percentage of previous period's dividend as restriction on current period dividends	103.00%
WPS \| Minimum \| Public Service Commission of Wisconsin (PSCW)
Dividend Payment Restrictions
Common equity ratio required to be maintained (as a percent)	51.00%

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

No definition available.

Name:	teg_CommonEquityRatioToBeMaintained
Namespace Prefix:	teg_
Data Type:	num:percentItemType
Balance Type:	na
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

- 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 maximum debt to capitalization ratio.

+ References

No definition available.

+ Details

Name:	teg_MaximumDebttoCapitalizationRatio
Namespace Prefix:	teg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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