Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	$ 432	$ 430
Incurred	55	20
Settled	(38)	(40)
Accretion	21	22
Cash Flow Revisions	7	0
ARO Liability, end of period	477	432
Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	428	429
Incurred	55	17
Settled	(37)	(40)
Accretion	21	22
Cash Flow Revisions	7	0
ARO Liability, end of period	474	428
Gas treating plant and gas wells
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	1	1
Incurred	0	0
Settled	(1)	0
Accretion	0	0
Cash Flow Revisions	0	0
ARO Liability, end of period	0	1
Coal ash disposal areas | Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	179	191
Incurred	0	0
Settled	(27)	(20)
Accretion	7	8
Cash Flow Revisions	7	0
ARO Liability, end of period	166	179
Gas distribution cut, purge, and cap | Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	205	186
Incurred	22	17
Settled	(8)	(9)
Accretion	12	11
Cash Flow Revisions	0	0
ARO Liability, end of period	231	205
Asbestos abatement | Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	33	42
Incurred	0	0
Settled	(1)	(11)
Accretion	2	2
Cash Flow Revisions	0	0
ARO Liability, end of period	34	33
Renewable generation assets
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	3	0
Incurred	0	3
Settled	0	0
Accretion	0	0
Cash Flow Revisions	0	0
ARO Liability, end of period	3	3
Renewable generation assets | Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	11	10
Incurred	10	0
Settled	0	0
Accretion	0	1
Cash Flow Revisions	0	0
ARO Liability, end of period	21	11
Gas wells plug and abandon | Consumers Energy Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO Liability, at beginning of period	0
Incurred	23
Settled	(1)
Accretion	0
Cash Flow Revisions	0
ARO Liability, end of period	$ 22	$ 0