SHORT-TERM DEBT AND LINES OF CREDIT - REVOLVING CREDIT FACILITIES (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Revolving credit facilities
Short-term credit capacity	$ 2,800.0
Letters of credit issued inside credit facilities	1.2
Commercial paper outstanding	1,200.3	$ 1,444.6
Available capacity under existing agreements	1,598.5
WEC Energy Group \| Credit facility maturing during October 2022
Revolving credit facilities
Short-term credit capacity	1,200.0
WE \| Credit facility maturing during October 2022
Revolving credit facilities
Short-term credit capacity	500.0
WPS \| Credit facility maturing during October 2022
Revolving credit facilities
Short-term credit capacity	400.0
WG \| Credit facility maturing during October 2022
Revolving credit facilities
Short-term credit capacity	350.0
PGL \| Credit facility maturing during October 2022
Revolving credit facilities
Short-term credit capacity	$ 350.0

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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)(a)(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: 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))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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)(2))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

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

+ References

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+ References

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- 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.

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- Definition

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

+ References

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