Retirement Benefits (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) year	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Union employees percentage	41.00%
Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Union employees percentage	42.00%
DB Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 22
Amortized net gains and losses in excess of PBO or MRV	10.00%
Period for gains or losses to be included in market related value	5 years
ABO	$ 2,000	$ 2,700
DB Pension Plans | Pension Costs
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	21
DB Pension Plans | Consumers Energy Company | Pension Costs
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 21
DB Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	50.00%
DB Pension Plans | Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	40.00%
DB Pension Plans | Real asset investments
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	10.00%
OPEB Plan
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 0	$ 0	$ 0
Retirement age requirement | year	55
Retirement years of service	10 years
Retirement years of service with disability	15 years
Ultimate health care cost trend rate	4.75%
Year health care cost trend rate reaches ultimate trend rate	2032
Estimated time of amortization of gains losses	9 years	9 years	9 years
OPEB Plan | Under Age 65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed next fiscal year	6.50%	6.25%
OPEB Plan | Over Age 65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed next fiscal year	6.75%
OPEB Plan | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Retirement age requirement | year	55
Retirement years of service	10 years
Retirement years of service with disability	15 years
Ultimate health care cost trend rate	4.75%
Year health care cost trend rate reaches ultimate trend rate	2032
OPEB Plan | Consumers Energy Company | Under Age 65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed next fiscal year	6.50%	6.25%
OPEB Plan | Consumers Energy Company | Over Age 65
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed next fiscal year	6.75%
Postretirement Health Trusts | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	51.00%
Postretirement Health Trusts | Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	39.00%
Postretirement Health Trusts | Real asset investments
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	10.00%
Postretirement Life Trusts | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	53.00%
Postretirement Life Trusts | Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	32.00%
Postretirement Life Trusts | Multi-asset investments
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage	15.00%
DB Pension Plan A Settlement | DB Pension Plans | Pension Costs
Defined Benefit Plan Disclosure [Line Items]
Regulatory asset, amortization period	8 years
Defined Company Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Plan cost, defined contribution plan	$ 48	$ 41	$ 31
Defined Company Contribution Plan | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Plan cost, defined contribution plan	48	41	31
DC SERP
Defined Benefit Plan Disclosure [Line Items]
Plan cost, defined contribution plan	$ 1	2	2
Minimum years of participation before vesting	5 years
Trust assets	$ 12	13
401 (K) Plan
Defined Benefit Plan Disclosure [Line Items]
Plan cost, defined contribution plan	44	31	29
401 (K) Plan | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Plan cost, defined contribution plan	$ 43	$ 31	$ 29
Pension Plan A | DB Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated time of amortization of gains losses	8 years	8 years	8 years
Estimated time of prior service cost			8 years
Pension Plan A | DB Pension Plans | Consumers Energy Company
Defined Benefit Plan Disclosure [Line Items]
Estimated time of prior service cost			8 years
Pension Plan B | DB Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Estimated time of amortization of gains (losses) life expectancy	18 years	18 years	19 years
Minimum | Defined Company Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Employer match of eligible wages	5.00%
Minimum | DC SERP
Defined Benefit Plan Disclosure [Line Items]
Plan contribution percentage	5.00%
Minimum | 401 (K) Plan
Defined Benefit Plan Disclosure [Line Items]
Employer match of eligible wages	4.00%
Maximum | Defined Company Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Employer match of eligible wages	10.00%
Maximum | DC SERP
Defined Benefit Plan Disclosure [Line Items]
Plan contribution percentage	15.00%
Maximum | 401 (K) Plan
Defined Benefit Plan Disclosure [Line Items]
Employer match of eligible wages	6.00%