Contingencies and Commitments (Contingencies And Commitments) (Details) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		29 Months Ended
	Sep. 30, 2020 USD ($)	May 30, 2020 USD ($)	Jun. 30, 2021 USD ($) site MW	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) site MW	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) site MW	Dec. 31, 2020 USD ($)
Loss Contingencies [Line Items]
Regulatory assets			$ 2,606,000		$ 2,606,000		$ 2,606,000	$ 2,653,000
Operating Revenue			1,558,000	$ 1,382,000	3,571,000	$ 3,184,000
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			2,606,000		2,606,000		2,606,000	$ 2,653,000
Cost of gas sold			94,000	80,000	372,000	350,000
Maintenance and other operating expenses			(339,000)	(302,000)	(631,000)	(580,000)
Operating Revenue			1,493,000	$ 1,330,000	3,430,000	$ 3,074,000
Consumers Energy Company | Manufactured Gas Plant
Loss Contingencies [Line Items]
Regulatory assets			115,000		115,000		115,000
Bay Harbor
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 44,000		$ 44,000		$ 44,000
Discounted projected costs rate			4.34%		4.34%		4.34%
Accrual for environmental loss contingencies, inflation rate			1.00%		1.00%		1.00%
Remaining undiscounted obligation amount			$ 55,000		$ 55,000		$ 55,000
CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000		3,000		3,000
CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000		3,000		3,000
CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			8,000		8,000		8,000
Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 56,000		$ 56,000		$ 56,000
Discounted projected costs rate			2.57%		2.57%		2.57%
Accrual for environmental loss contingencies, inflation rate			2.50%		2.50%		2.50%
Remaining undiscounted obligation amount			$ 61,000		$ 61,000		$ 61,000
Number of former MGPs | site			23		23		23
Regulatory asset collection period					10 years
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			$ 3,000		$ 3,000		$ 3,000
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000		3,000		3,000
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			4,000		4,000		4,000
Gas Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			1,000		1,000		1,000
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies			3,000		3,000		3,000
Equatorial Guinea Tax Claim
Loss Contingencies [Line Items]
Foreign government tax claim on sale			152,000		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			10,000		10,000		10,000
Ray Compressor Station | Consumers Energy Company | Repair Costs
Loss Contingencies [Line Items]
Insurance recoveries			7,000		7,000		7,000
Ray Compressor Station | Consumers Energy Company | Incremental Gas Purchases
Loss Contingencies [Line Items]
Insurance recoveries			$ 3,000		3,000		$ 3,000
Ray Compressor Station | Consumers Energy Company | Insurance Recoveries
Loss Contingencies [Line Items]
Reduction to plant, property and equipment					4,000
Maintenance and other operating expenses					3,000
Operating Revenue					$ 3,000
Ray Compressor Station | Consumers Energy Company | GCR underrecoveries
Loss Contingencies [Line Items]
Cost of gas sold	$ 7,000
New Covert Generating Facility | Consumers Energy Company
Loss Contingencies [Line Items]
Nameplate capacity (in MW) | MW			1,176		1,176		1,176
Long-term purchase commitment, amount					$ 810,000
Enterprise Segment Generating Units | Consumers Energy Company
Loss Contingencies [Line Items]
Nameplate capacity (in MW) | MW			1,001		1,001		1,001
Long-term purchase commitment, amount					$ 515,000