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Short-Term Debt and Lines of Credit - Outstanding Amounts (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Short-term Debt [Line Items] |  |
Commercial paper | $ 1,440.1 | $ 1,444.6
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% |
WEC Energy Group |  |
Short-term Debt [Line Items] |  |
Commercial paper | $ 548.4 | 494.8
Maximum debt to capitalization ratio | 70.00% |
Commercial paper |  |
Short-term Debt [Line Items] |  |
Commercial paper | $ 1,440.1 | $ 1,444.6
Average interest rate on amount outstanding | 2.92% | 1.77%
Average amount outstanding during the year | $ 1,350.7 |
Weighted Average interest rate during the year | 2.32% |

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