Asset Retirement Obligations (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 340
Incurred
Settled	$ (3)
Accretion	14
Cash flow Revisions	68
ARO Liability, end of period	419
Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 339
Incurred
Settled	$ (3)
Accretion	14
Cash flow Revisions	68
ARO Liability, end of period	418
Close Gas Treating Plant and Gas Wells [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 1
Incurred
ARO Liability, end of period	$ 1
Coal Ash Disposal Areas [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 120
Incurred
Accretion	$ 4
Cash flow Revisions	68
ARO Liability, end of period	192
Asbestos Abatement [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 51
Incurred
Accretion	$ 2
ARO Liability, end of period	53
Gas Distribution Cut, Purge, Cap [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 162
Incurred
Settled	$ (3)
Accretion	8
ARO Liability, end of period	167
Wind Park [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 6
Incurred
ARO Liability, end of period	$ 6