Name:	teg_DisposalGroupAccumulatedDeferredInvestmentTaxCredit
Namespace Prefix:	teg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The noncurrent portion of the carrying amount of a liability for an asset retirement obligation included in a disposal group held for sale or disposed of.

No definition available.

Name:	teg_DisposalGroupAssetRetirementObligation
Namespace Prefix:	teg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The carrying amount of an investment in an equity method investee included in a disposal group held for sale or disposed of.

No definition available.

Name:	teg_DisposalGroupEquityMethodInvestment
Namespace Prefix:	teg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

For the disposal group, including a component of the entity (discontinued operation), accumulated depreciation of property, plant and equipment.

No definition available.

Name:	teg_DisposalGroupIncludingDiscontinuedOperationAccumulatedDepreciation
Namespace Prefix:	teg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the period for which transition services are provided, following the sale of business.

No definition available.

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

Amount classified as assets attributable to disposal group held for sale or disposed of.

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

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationBalanceSheetDisclosuresAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount classified as other assets attributable to disposal group held for sale or disposed of, expected to be disposed of after one year or the normal operating cycle, if longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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

Amount classified as property, plant and equipment attributable to disposal group held for sale or disposed of, expected to be disposed of after one year or the normal operating cycle, if longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1436-107760

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=8077374&loc=d3e2510-110228

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

Name:	us-gaap_DisposalGroupNotDiscontinuedOperationDisposalDisclosuresAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount classified as liabilities attributable to disposal group held for sale or disposed of.

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

Amount classified as liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.

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

Amount classified as liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of beyond one year or the normal operating cycle, if longer.

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

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

Name:	us-gaap_ProceedsFromDivestitureOfBusinesses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Name:	us-gaap_StatementBusinessSegmentsAxis=teg_ElectricUtilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: