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 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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

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Short-term Debt and Lines of Credit - Revolving Credit Facilities (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,300.0
Letters of credit issued inside credit facilities	18.0
Commercial Paper	661.5	$ 617.6
Available capacity under existing agreements	1,620.5
WEC Energy Group Credit Facility Expiring December 2019 [Member]
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	400.0
Wisconsin Electric Credit Facility expiring December 2019 [Member]
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	500.0
Wisconsin Gas Credit facility expiring December 2019 [Member]
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	350.0
Revolving Credit Facility maturing June 13, 2017 [Member] \| Integrys Holding
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	285.0
Revolving Credit Facility maturing June 13, 2017 [Member] \| WPS
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	115.0
Revolving Credit Facility maturing June 13, 2017 [Member] \| PGL
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	250.0
Revolving credit facility maturing on May 8, 2019 \| Integrys Holding
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	265.0
Revolving credit facility maturing on May 8, 2019 \| WPS
Short-term borrowings
Line of Credit Facility, Maximum Borrowing Capacity	135.0
Commercial paper
Short-term borrowings
Commercial Paper	$ 661.5