Contingencies and Commitments (Contingencies And Commitments) (Details) $ in Thousands	1 Months Ended		3 Months Ended		26 Months Ended
	Sep. 30, 2020 USD ($)	May 30, 2020 USD ($)	Mar. 31, 2021 USD ($) site	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) site	Dec. 31, 2020 USD ($)
Loss Contingencies [Line Items]
Regulatory assets			$ 2,613,000		$ 2,613,000	$ 2,653,000
Operating Revenue			2,083,000	$ 1,864,000
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			2,613,000		2,613,000	$ 2,653,000
Cost of gas sold			278,000	270,000
Maintenance and other operating expenses			(292,000)	(278,000)
Operating Revenue			1,937,000	$ 1,744,000
Consumers Energy Company | Manufactured Gas Plant
Loss Contingencies [Line Items]
Regulatory assets			118,000		118,000
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			$ 56,000		$ 56,000
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			$ 56,000		$ 56,000
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			10,000		10,000
Ray Compressor Station | Consumers Energy Company | Repair Costs
Loss Contingencies [Line Items]
Insurance recoveries			7,000		7,000
Ray Compressor Station | Consumers Energy Company | Incremental Gas Purchases
Loss Contingencies [Line Items]
Insurance recoveries			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