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Summary of Significant Accounting Policies Cash and Cash Equivalents (Details) | 12 Months Ended
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Dec. 31, 2017
Accounting Policies [Abstract] |
Maximum term of original maturity to classify instrument as cash equivalent | 3 months

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- References No definition available. + Details
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- Definition Maximum term of original maturity to classify an instrument as a cash equivalent. + References No definition available. + Details
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Namespace Prefix: | wec_
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