Total costs accrued as of the balance sheet date for environmental loss contingencies.

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The capital and operating costs needed to achieve the required level of reduction in emissions.

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COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details) $ in Millions	1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 31, 2014 compliance_option	Sep. 30, 2017 USD ($)	Dec. 31, 2015	Dec. 31, 2016 USD ($)	Sep. 30, 2016 Case
Climate Change \| Electric
Air quality
Number of legal cases heard by a court \| Case					1
Percentage of nationwide greenhouse gas emissions reduction			32.00%
Interim goal for greenhouse gas emissions reduction (fraction)			0.667
Company goal for percentage of carbon dioxide emissions reduction		40.00%
Climate Change \| Electric \| Wisconsin
Air quality
Percentage of greenhouse gas emissions reduction by state			41.00%
Climate Change \| Electric \| Michigan
Air quality
Percentage of greenhouse gas emissions reduction by state			39.00%
Clean Water Act Cooling Water Intake Structure Rule \| Electric
Water quality
Number of compliance options available to meet standard \| compliance_option	7
Steam Electric Effluent Limitation Guidelines \| Electric
Water quality
Renewal period for facility permits		5 years
Steam Electric Effluent Limitation Guidelines \| Electric \| Minimum
Water quality
Expected cost to achieve required emissions reductions		$ 80.0
Steam Electric Effluent Limitation Guidelines \| Electric \| Maximum
Water quality
Expected cost to achieve required emissions reductions		110.0
Manufactured Gas Plant Remediation \| Natural gas
Manufactured gas plant remediation
Regulatory assets recorded for remediation of manufactured gas plant sites		683.3		$ 702.7
Reserves recorded for remediation of manufactured gas plant sites		$ 617.5		$ 633.4