Represents the maximum debt to capitalization ratio.

No definition available.

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Period Type:	duration

- Definition

Maximum percentage of Junior Subordinated Notes that can be redeemed or repurchased without replacement within 360 days.

+ References

No definition available.

+ Details

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- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond 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

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+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

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-Topic 835

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+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher SEC

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Subparagraph (SX 210.7-03.16)

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

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ 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 210.5-02.19,20)

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-Name Regulation S-X (SX)

-Number 210

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-Name Regulation S-X (SX)

-Number 210

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+ Details

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

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ 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 210.5-02.22)

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
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- Details

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- Details

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- Details

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LONG-TERM DEBT (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	1 Months Ended
	Dec. 31, 2014	Nov. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Nov. 01, 2014	Jun. 01, 2014
LONG-TERM DEBT
Total	$ 3,081.9us-gaap_DebtInstrumentCarryingAmount			$ 3,056.9us-gaap_DebtInstrumentCarryingAmount
Unamortized discount on debt	(0.6)			(0.7)
Total debt	3,081.3us-gaap_LongTermDebt			3,056.2us-gaap_LongTermDebt
Less current portion	125.0us-gaap_LongTermDebtCurrent			100.0us-gaap_LongTermDebtCurrent
Total long-term debt	2,956.3us-gaap_LongTermDebtNoncurrent			2,956.2us-gaap_LongTermDebtNoncurrent
Debt to capitalization ratio required to be maintained (as a percent)	65.00%teg_MaximumDebttoCapitalizationRatio
WPS
LONG-TERM DEBT
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
WPS \| First Mortgage Bonds
LONG-TERM DEBT
Interest rate stated percentage	7.125%
Total	0.1			0.1
WPS \| Senior Notes, 6.375% due 2015
LONG-TERM DEBT
Interest rate stated percentage	6.375%
Total	125.0			125.0
Less current portion	125.0
WPS \| Senior Notes, 5.65% due 2017
LONG-TERM DEBT
Interest rate stated percentage	5.65%
Total	125.0			125.0
WPS \| Senior Notes, 6.08% due 2028
LONG-TERM DEBT
Interest rate stated percentage	6.08%
Total	50.0			50.0
WPS \| Senior Notes, 5.55% due 2036
LONG-TERM DEBT
Interest rate stated percentage	5.55%
Total	125.0			125.0
WPS \| Senior Notes, 3.671% due 2042
LONG-TERM DEBT
Interest rate stated percentage	3.671%
Total	300.0			300.0
WPS \| Senior Notes, 4.752% due 2044
LONG-TERM DEBT
Interest rate stated percentage	4.752%
Total	450.0			450.0
PGL
LONG-TERM DEBT
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
PGL \| Fixed First and Refunding Mortgage Bonds, Series QQ, 4.875% bonds due 2038
LONG-TERM DEBT
Interest rate stated percentage	4.875%				4.875%
Total	0			75.0
Principal balance repaid		75.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series RR, 4.30% bonds due 2035
LONG-TERM DEBT
Interest rate stated percentage	4.30%
Total	50.0			50.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series TT, 8.00% bonds due 2018
LONG-TERM DEBT
Interest rate stated percentage	8.00%
Total	5.0			5.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series UU, 4.63% bonds due 2019
LONG-TERM DEBT
Interest rate stated percentage	4.63%
Total	75.0			75.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series VV, 3.900% bonds due 2030
LONG-TERM DEBT
Interest rate stated percentage	3.90%
Total	50.0			50.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series WW, 2.625% bonds due 2033
LONG-TERM DEBT
Interest rate stated percentage	2.625%
Total	50.0			50.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series XX, 2.21% bonds due 2016
LONG-TERM DEBT
Interest rate stated percentage	2.21%
Total	50.0			50.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series YY, 3.98% bonds due 2042
LONG-TERM DEBT
Interest rate stated percentage	3.98%
Total	100.0			100.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series ZZ, 4.00% bonds due 2033
LONG-TERM DEBT
Interest rate stated percentage	4.00%
Total	50.0			50.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series AAA, 3.96% bonds due 2043
LONG-TERM DEBT
Interest rate stated percentage	3.96%
Total	220.0			220.0
PGL \| Fixed First and Refunding Mortgage Bonds, Series BBB, 4.21% bonds due 2044 [Member]
LONG-TERM DEBT
Interest rate stated percentage	4.21%	4.21%
Total	200.0			0
Amount of debt issued		200.0
NSG \| First Mortgage Series P, 3.43% bonds due 2027
LONG-TERM DEBT
Interest rate stated percentage	3.43%
Total	28.0			28.0
NSG \| First Mortgage Series Q, 3.96% bonds due 2043
LONG-TERM DEBT
Interest rate stated percentage	3.96%
Total	54.0			54.0
Integrys Energy Group, Inc.
LONG-TERM DEBT
Less current portion	0			100.0
Total long-term debt	974.7			974.7
Debt to capitalization ratio required to be maintained (as a percent)	65.00%
Integrys Energy Group, Inc. \| Unsecured Senior Notes, 7.27% due 2014
LONG-TERM DEBT
Interest rate stated percentage	7.27%					7.27%
Total	0			100.0
Principal balance repaid			100.0
Integrys Energy Group, Inc. \| Unsecured Senior Notes, 8.00% due 2016
LONG-TERM DEBT
Interest rate stated percentage	8.00%
Total	55.0			55.0
Integrys Energy Group, Inc. \| Unsecured Senior Notes, 4.17% due 2020
LONG-TERM DEBT
Interest rate stated percentage	4.17%
Total	250.0			250.0
Integrys Energy Group, Inc. \| Junior Subordinated Notes, 6.11% due 2066
LONG-TERM DEBT
Interest rate stated percentage	6.11%
Total	269.8			269.8
Maximum percentage of notes that can be redeemed or repurchased without replacement	10.00%
Integrys Energy Group, Inc. \| Junior Subordinated Notes, 6.00% due 2073
LONG-TERM DEBT
Interest rate stated percentage	6.00%
Total	$ 400.0			$ 400.0