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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SHORT-TERM DEBT AND LINES OF CREDIT - REVOLVING CREDIT FACILITIES (Details) - USD ($) $ in Millions	Oct. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Line of Credit Facility
Short-term credit capacity		$ 2,500.0
Letters of credit issued inside credit facilities		32.9
Commercial Paper		993.5	$ 860.2
Available capacity under existing agreements		1,473.6
WEC Energy Group \| Credit facility maturing December 2020
Line of Credit Facility
Short-term credit capacity		1,050.0
WE \| Credit facility maturing December 2020
Line of Credit Facility
Short-term credit capacity		500.0
WPS \| Credit facility maturing December 2020
Line of Credit Facility
Short-term credit capacity		250.0
WG \| Credit facility maturing December 2020
Line of Credit Facility
Short-term credit capacity		350.0
PGL \| Credit facility maturing December 2020
Line of Credit Facility
Short-term credit capacity		$ 350.0
Subsequent event \| WEC Energy Group \| Credit facility maturing October 2022
Line of Credit Facility
Short-term credit capacity	$ 1,200.0
Subsequent event \| WE \| Credit facility maturing October 2022
Line of Credit Facility
Short-term credit capacity	500.0
Subsequent event \| WPS \| Credit facility maturing October 2022
Line of Credit Facility
Short-term credit capacity	400.0
Subsequent event \| WG \| Credit facility maturing October 2022
Line of Credit Facility
Short-term credit capacity	350.0
Subsequent event \| PGL \| Credit facility maturing October 2022
Line of Credit Facility
Short-term credit capacity	$ 350.0