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Short-Term Debt and Lines of Credit - Outstanding Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Commercial paper	$ 1,444.6	$ 860.2
WEC Energy Group
Short-term Debt [Line Items]
Commercial paper	$ 494.8	$ 321.8
Maximum debt to capitalization ratio	70.00%
WE
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
WPS
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
WG
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
PGL
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
Commercial paper
Short-term Debt [Line Items]
Commercial paper	$ 1,444.6
Average interest rate on amount outstanding	1.77%	0.96%
Average amount outstanding during the year	$ 833.8
Weighted Average interest rate during the year	1.34%

X

- Definition

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.

+ 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)(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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+ References

No definition available.

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- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

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

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For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period.

+ References

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Commercial Paper Weighted Average Interest Rate

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- Definition

Represents the maximum debt to capitalization ratio.

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