Schedule I - Future Maturities of Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Future maturities of long-term debt outstanding
2018	$ 836.1
2020	684.4
Thereafter	6,953.5
Total	9,322.4
Long-term notes outstanding	9,158.2	$ 9,124.1
WECC
Future maturities of long-term debt outstanding
Long-term notes outstanding	50.0
WEC Energy Group
Future maturities of long-term debt outstanding
2018	300.0
2020	400.0
Thereafter	1,200.0
Total	1,900.0
Long-term notes outstanding	$ 1,890.0	$ 1,887.2