Short-term Debt and Lines of Credit - Revolving Credit Facilities (Details) - USD ($) $ in Millions |
Mar. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Line of Credit Facility [Line Items] | ||
| Short-term credit capacity | $ 2,500.0 | |
| Letters of credit issued inside credit facilities | 18.0 | |
| Commercial Paper | 896.4 | $ 1,095.0 |
| Available capacity under existing agreements | 1,585.6 | |
| WEC Energy Group | Credit facility maturing December 2020 | ||
| Line of Credit Facility [Line Items] | ||
| Short-term credit capacity | 1,050.0 | |
| Wisconsin Electric | Credit facility maturing December 2020 | ||
| Line of Credit Facility [Line Items] | ||
| Short-term credit capacity | 500.0 | |
| WPS | Credit facility maturing December 2016 | ||
| Line of Credit Facility [Line Items] | ||
| Short-term credit capacity | 250.0 | |
| Wisconsin Gas | Credit facility maturing December 2020 | ||
| Line of Credit Facility [Line Items] | ||
| Short-term credit capacity | 350.0 | |
| PGL | Credit facility maturing December 2020 | ||
| Line of Credit Facility [Line Items] | ||
| Short-term credit capacity | $ 350.0 |