Summary of Significant Accounting Policies Property, Plant and Equipment (Details)	6 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Wisconsin Electric
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)		3.00%	3.00%	3.00%
WPS
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)	1.00%
Wisconsin Gas
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)		2.00%	3.00%	3.00%
PGL
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)	1.67%
NSG
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)	1.22%
MERC
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)	1.26%
MGU
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility composite depreciation rate (as a percent)	1.32%
Maximum | PWGS 1 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P45Y
Maximum | PWGS 2 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P45Y
Maximum | OC 1 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P55Y
Maximum | OC 2 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P55Y
Maximum | Software [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P15Y
Minimum | PWGS 1 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P10Y
Minimum | PWGS 2 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P10Y
Minimum | OC 1 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P10Y
Minimum | OC 2 [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P10Y
Minimum | Software [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation over an estimated useful life		P3Y