Dispositions (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dispositions
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			$ 19.6	$ 22.9	$ 7.5
Wisconsin | WE
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
DisposalGroupNotDiscontinuedOperationsAftertaxGainLossOnDisposal	$ 6.5
Corporate and Other | Wisvest [Member]
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
DisposalGroupNotDiscontinuedOperationsAftertaxGainLossOnDisposal	11.8
Corporate and Other | ITF
Dispositions
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		$ 0.0
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Accounts receivable and unbilled revenues				37.2
Materials, supplies, and inventories				34.9
Other current assets				18.4
Property, plant, and equipment				2.6
Other long-term assets				3.7
Total assets				96.8
Accounts payable				12.9
Accrued payroll and benefits				2.4
Other current liabilities				4.5
Pension and OPEB obligations				1.2
Other long-term liabilities				0.6
Total liabilities				$ 21.6
Operating Expense [Member] | Wisconsin | WE
Dispositions
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	10.9
Other Income [Member] | Corporate and Other | Wisvest [Member]
Dispositions
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	$ 19.6