Contingencies and Commitments (Contingencies And Commitments) (Details) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended	24 Months Ended
	Sep. 30, 2020 USD ($)	Mar. 31, 2022 USD ($) site	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items]
Regulatory assets		$ 2,138		$ 2,259	$ 2,259
Operating Revenue		2,374	$ 2,013
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets		2,138		2,259	2,259
Cost of gas sold		465	278
Maintenance and other operating expenses		(313)	(292)
Operating Revenue		2,283	$ 1,937
Consumers Energy Company | Tax And Other Indemnity Obligations
Loss Contingencies [Line Items]
Carrying value of indemnity obligations		1
Consumers Energy Company | Manufactured Gas Plant
Loss Contingencies [Line Items]
Regulatory assets		109
Bay Harbor
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		$ 45
Discounted projected costs rate		4.34%
Accrual for environmental loss contingencies, inflation rate		1.00%
Remaining undiscounted obligation amount		$ 56
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
Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		$ 57
Discounted projected costs rate		2.57%
Accrual for environmental loss contingencies, inflation rate		2.50%
Remaining undiscounted obligation amount		$ 61
Number of former MGPs | site		23
Regulatory asset collection period		10 years
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		$ 2
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs		2
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs		4
Gas Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		1
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies		3
Ray Compressor Station | Consumers Energy Company
Loss Contingencies [Line Items]
Plant additions					$ 17
Insurance recoveries received		$ 13
Ray Compressor Station | Consumers Energy Company | Insurance Recoveries
Loss Contingencies [Line Items]
Reduction to plant, property and equipment				6
Maintenance and other operating expenses				3
Operating Revenue				$ 4
Ray Compressor Station | Consumers Energy Company | GCR underrecoveries
Loss Contingencies [Line Items]
Cost of gas sold	$ 7