Represents the maximum debt to capitalization ratio.

No definition available.

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Amount of increase (decrease) of the credit facility.

+ 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.(f))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph f

-Article 4

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph a

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),16(a)(1))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Subparagraph a(1)

-Article 7

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13

-Subparagraph 2, 3

-Article 9

+ Details

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

- Details

Name:	us-gaap_ShortTermDebtLineItems
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Balance Type:	na
Period Type:	duration

- Details

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- Details

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- Details

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- Details

Name:	us-gaap_ShortTermDebtTypeAxis=teg_RevolvingCreditFacilityMaturingMay172014Member
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- Details

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- Details

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- Details

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- Details

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- Details

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SHORT-TERM DEBT AND LINES OF CREDIT CAPACITY (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Short-term borrowings
Total short-term credit capacity	$ 1,250.0	$ 1,250.0	$ 1,610.0
Letters of credit issued inside credit facilities	3.4	3.4	52.4
Short-term borrowings outstanding	317.6us-gaap_ShortTermBorrowings	317.6us-gaap_ShortTermBorrowings	326.0us-gaap_ShortTermBorrowings
Available capacity under existing agreements	929.0	929.0	1,231.6
Decrease Line of Credit Facility, Net	350
Debt to capitalization ratio required to be maintained (as a percent)		65.00%teg_MaximumDebttoCapitalizationRatio
Integrys Energy Group, Inc.
Short-term borrowings
Short-term borrowings outstanding	7.2	7.2	123.2
Debt to capitalization ratio required to be maintained (as a percent)		65.00%
WPS
Short-term borrowings
Debt to capitalization ratio required to be maintained (as a percent)		65.00%
PGL
Short-term borrowings
Debt to capitalization ratio required to be maintained (as a percent)		65.00%
Revolving credit facility maturing on May 17, 2014 \| Integrys Energy Group, Inc.
Short-term borrowings
Total short-term credit capacity	0	0	275.0
Revolving credit facility maturing on May 17, 2014 \| WPS
Short-term borrowings
Total short-term credit capacity	0	0	135.0
Revolving credit facility maturing on May 17, 2016 \| Integrys Energy Group, Inc.
Short-term borrowings
Total short-term credit capacity	0	0	200.0
Revolving credit facility maturing on June 13, 2017 \| Integrys Energy Group, Inc.
Short-term borrowings
Total short-term credit capacity	285.0	285.0	635.0
Revolving credit facility maturing on June 13, 2017 \| WPS
Short-term borrowings
Total short-term credit capacity	115.0	115.0	115.0
Revolving credit facility maturing on June 13, 2017 \| PGL
Short-term borrowings
Total short-term credit capacity	250.0	250.0	250.0
Revolving credit facility maturing on May 8, 2019 \| Integrys Energy Group, Inc.
Short-term borrowings
Total short-term credit capacity	465.0	465.0	0
Revolving Credit Facility Maturing May 7, 2015 \| WPS
Short-term borrowings
Total short-term credit capacity	135.0	135.0	0
Commercial paper
Short-term borrowings
Short-term borrowings outstanding	$ 317.6	$ 317.6	$ 326.0	$ 482.4