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Short-Term Debt and Lines of Credit - Outstanding Amounts (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Short-term Debt [Line Items] |  |  |
Issuance of short-term loan | $ 340.0 | $ 0.0 | $ 0.0
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 outstanding | $ 820.4 | 334.7 |
Issuance of short-term loan | $ 340.0 | 0.0 | $ 0.0
Maximum debt to capitalization ratio | 70.00% |  |
Commercial paper |  |  |
Short-term Debt [Line Items] |  |  |
Commercial paper outstanding | $ 1,436.9 | $ 830.8 |
Average interest rate on amount outstanding | 0.21% | 2.00% |
Average amount outstanding during the year | $ 788.9 |  |
Weighted- average interest rate during the year | 0.85% |  |
Term loan |  |  |
Short-term Debt [Line Items] |  |  |
Average interest rate on amount outstanding | 0.99% | 0.00% |
Term loan outstanding | $ 340.0 | $ 0.0 |
Weighted- average interest rate during the year | 1.38% |  |
Issuance of short-term loan | $ 340.0 |  |
Length of term loan | 364 days |  |

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