Contingencies and Commitments (Contingencies And Commitments) (Details) $ in Thousands	1 Months Ended		3 Months Ended								12 Months Ended
	Sep. 30, 2020 USD ($)	May 31, 2020 USD ($)	Dec. 31, 2021 USD ($) site	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($) site	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Loss Contingencies [Line Items]
Regulatory assets			$ 2,259,000				$ 2,653,000				$ 2,259,000		$ 2,653,000
Operating Revenue			2,033,000	$ 1,725,000	$ 1,558,000	$ 2,013,000	1,727,000	$ 1,507,000	$ 1,382,000	$ 1,802,000	7,329,000		6,418,000		$ 6,624,000
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			2,259,000				2,653,000				2,259,000		2,653,000
Cost of gas sold											726,000		568,000		754,000
Plant additions											2,400,000		2,000,000
Maintenance and other operating expenses											(1,531,000)		(1,224,000)		(1,275,000)
Operating Revenue											7,021,000		6,189,000		$ 6,376,000
Consumers Energy Company | Manufactured Gas Plant
Loss Contingencies [Line Items]
Regulatory assets			112,000				$ 120,000				112,000		$ 120,000
Consumers Energy Company | GCR underrecoveries
Loss Contingencies [Line Items]
Cost of gas sold												$ 400,000		$ 500,000
Bay Harbor
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 45,000								$ 45,000
Discounted projected costs rate			4.34%								4.34%
Accrual for environmental loss contingencies, inflation rate			1.00%								1.00%
Remaining undiscounted obligation amount			$ 57,000								$ 57,000
CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000								3,000
CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000								3,000
CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			8,000								8,000
Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 57,000								$ 57,000
Discounted projected costs rate			2.57%								2.57%
Accrual for environmental loss contingencies, inflation rate			2.50%								2.50%
Remaining undiscounted obligation amount			$ 61,000								$ 61,000
Number of former MGPs | site			23								23
Regulatory asset collection period											10 years
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 2,000								$ 2,000
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			2,000								2,000
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			4,000								4,000
Gas Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			1,000								1,000
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000								3,000
Equatorial Guinea Tax Claim
Loss Contingencies [Line Items]
Foreign government tax claim on sale			152,000								152,000
Civil Case, Consumers V. MPSC Staff | Consumers Energy Company
Loss Contingencies [Line Items]
Civil penalty		$ 10
Ray Compressor Station | Consumers Energy Company
Loss Contingencies [Line Items]
Plant additions											17,000
Insurance recoveries			$ 13,000								13,000
Ray Compressor Station | Consumers Energy Company | Insurance Recoveries
Loss Contingencies [Line Items]
Reduction to plant, property and equipment											6,000
Maintenance and other operating expenses											3,000
Operating Revenue											$ 4,000
Ray Compressor Station | Consumers Energy Company | GCR underrecoveries
Loss Contingencies [Line Items]
Cost of gas sold	$ 7,000