Regulatory Environment (Details) $ in Millions	1 Months Ended
	Oct. 31, 2016 USD ($)	Aug. 31, 2016 USD ($) MW	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)
WPS | Public Service Commission of Wisconsin (PSCW) | 2016 Rates
Regulatory environment
Approved return on equity (as a percent)				10.00%
Approved common equity component average (as a percent)				51.00%
WPS | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Electric rates
Regulatory environment
Approved annual rate increase (decrease)				$ (7.9)
Approved annual rate increase (decrease), percentage				(0.80%)
Authorized revenue requirement for ReACT			$ 275.0	$ 275.0
Percent fuel costs can vary from the rate case approved costs before deferral is required				2.00%
WPS | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Natural gas rates
Regulatory environment
Approved annual rate increase (decrease)				$ (6.2)
Approved annual rate increase (decrease), percentage				(2.10%)
MERC | Minnesota Public Utilities Commission (MPUC) | 2016 Rates | Natural gas rates
Regulatory environment
Interim rates to be refunded to customers					$ 1.9
UMERC
Regulatory environment
Term of electric power purchase agreement		20 years
Capacity of natural gas generating facility | MW		170
Estimated cost to construct power plant		$ 255.0
Estimated percent of power plant cost recovery from Tilden Mining Company		50.00%
Estimated percent of power plant cost recovery from utility customers		50.00%
Subsequent Event | MERC | Minnesota Public Utilities Commission (MPUC) | 2016 Rates | Natural gas rates
Regulatory environment
Approved return on equity (as a percent)	9.11%
Approved common equity component average (as a percent)	50.32%
Approved annual rate increase (decrease)	$ 6.8
Approved annual rate increase (decrease), percentage	3.00%
Number of years decoupling mechanism approved for	3 years