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Summary of Significant Accounting Policies AFUDC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Funds Used During Construction
AFUDC - Debt	$ 4.9	$ 10.9	$ 8.6
AFUDC - Equity	$ 11.4	$ 25.1	$ 20.1
WE
Allowance for Funds Used During Construction
Percentage of retail jurisdictional construction work in progress expenditure subject to public utilities allowance for funds used during construction calculation	50.00%
WPS
Allowance for Funds Used During Construction
Percentage of retail jurisdictional construction work in progress expenditure subject to public utilities allowance for funds used during construction calculation	50.00%
WBS
Allowance for Funds Used During Construction
Percentage of retail jurisdictional construction work in progress expenditure subject to public utilities allowance for funds used during construction calculation	50.00%
WG
Allowance for Funds Used During Construction
Percentage of retail jurisdictional construction work in progress expenditure subject to public utilities allowance for funds used during construction calculation	50.00%
Retail operations | WE
Allowance for Funds Used During Construction
Interest rate on accrued AFUDC	8.45%
Retail operations | WPS
Allowance for Funds Used During Construction
Interest rate on accrued AFUDC	7.72%
Retail operations | WBS
Allowance for Funds Used During Construction
Interest rate on accrued AFUDC	7.72%
Retail operations | WG
Allowance for Funds Used During Construction
Interest rate on accrued AFUDC	8.33%
Wholesale operations | WE
Allowance for Funds Used During Construction
Interest rate on accrued AFUDC	5.94%
Wholesale operations | WPS
Allowance for Funds Used During Construction
Interest rate on accrued AFUDC	1.01%

X

- Definition

The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

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X

- Definition

Amount capitalized of allowance for funds used during construction.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430

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X

- Definition

Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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X

- Definition

Represents the percentage of retail jurisdictional construction work in progress expenditures subject to the AFUDC calculation.

+ References

No definition available.

+ Details

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