Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	$ 447	$ 439
Incurred	5	3
Settled	(45)	(18)
Accretion	23	23
ARO Liability, end of period	430	447
Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	446	438
Incurred	5	3
Settled	(45)	(18)
Accretion	23	23
ARO Liability, end of period	429	446
Gas Treating Plant and Gas Wells [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	1	1
Incurred
Settled
Accretion
Cash flow Revisions
ARO Liability, end of period	1	1
Coal Ash Disposal Areas [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	201	200
Settled	(18)	(8)
Accretion	8	9
ARO Liability, end of period	191	201
Gas Distribution Cut, Purge, And Cap [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	182	178
Incurred	3	2
Settled	(11)	(9)
Accretion	12	11
ARO Liability, end of period	186	182
Asbestos Abatement [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	56	54
Settled	(16)	(1)
Accretion	2	3
ARO Liability, end of period	42	56
Renewable Generation Assets [Member] | Consumers Energy Company [Member]
Asset Retirement Obligations [Line Items]
ARO Liability, at beginning of period	7	6
Incurred	2	1
Settled
Accretion	1
Cash flow Revisions
ARO Liability, end of period	$ 10	$ 7