Contingencies and Commitments (Narrative) (Details) $ in Millions	1 Months Ended		9 Months Ended
	Jul. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) site	Dec. 31, 2022 USD ($)
Loss Contingencies [Line Items]
Environmental Loss Contingency, Statement Of Financial Position, Extensible Enumeration, Not Disclosed Flag			recorded liability
Regulatory assets			$ 3,793	$ 3,595
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			3,793	$ 3,595
Consumers Energy Company | MGP Sites
Loss Contingencies [Line Items]
Regulatory assets			$ 102
Consumers Energy Company | Ludington
Loss Contingencies [Line Items]
Ownership share			51.00%
Consumers Energy Company | Ludington Plant Overhaul Contract Dispute
Loss Contingencies [Line Items]
Damages sought		$ 15
Consumers Energy Company | J.H. Campbell 3 Plant Retirement Contract Dispute
Loss Contingencies [Line Items]
Damages sought	$ 37
Bay Harbor
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 44
Discount rate			4.34%
Accrual for environmental loss contingencies, inflation rate			1.00%
Accrual for environmental loss contingencies, gross			$ 54
NREPA | Electric Utility | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			2
NREPA | Gas Utility | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			1
NREPA | Minimum | Electric Utility | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			2
NREPA | Maximum | Electric Utility | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			4
NREPA | Maximum | Gas Utility | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3
CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3
CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3
CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			8
MGP Sites | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 63
Number of former MGPs | site			23
Regulatory asset collection period			10 years