Regulatory Matters (Narrative) (Details)	1 Months Ended
	Apr. 30, 2016 USD ($) item	Jan. 31, 2016 USD ($)	Nov. 30, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Dec. 31, 2015 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory liability current							$ 76,000,000		$ 82,000,000
Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liability current							$ 76,000,000		82,000,000
Electric Rate Case [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Annual rate increase requested						$ 163,000,000
Rate of return on equity requested						10.70%
Annual rate increase self-implemented					$ 110,000,000
Rate of return on equity authorized			10.30%
Temporary rate increase			$ 165,000,000
Electric Rate Case [Member] | Consumers Energy Company [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Annual rate increase authorized	$ 126,000,000
Number of units retired | item	7
Electric Rate Case [Member] | Self-Implemented Rate Refunds [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory liability current								$ 0
Gas Rate Case [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Annual rate increase requested				$ 85,000,000
Rate of return on equity requested				10.70%
Annual rate increase self-implemented		$ 60,000,000
Gas Rate Case [Member] | Consumers Energy Company [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Annual rate increase authorized	$ 40,000,000
Energy Optimization Plan Incentive [Member] | Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Requested recovery/collection									$ 18,000,000