Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	$ 42	$ 33
Regulatory assets, noncurrent	2,653	2,489
Regulatory liabilities, current	151	87
Regulatory liability, noncurrent	3,744	3,742
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	42	33
Regulatory assets, noncurrent	2,653	2,489
Total regulatory assets	2,695	2,522
Regulatory liabilities, current	151	87
Regulatory liability, noncurrent	3,744	3,742
Total regulatory liabilities	3,895	3,829
Income taxes, net | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	105	65
Regulatory liability, noncurrent	1,419	1,510
Reserve for customer refunds | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	28	2
Gain shared with customers | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	14	17
Other | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	4	3
Regulatory liability, noncurrent	11	11
Cost of removal | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	2,245	2,126
Renewable energy grant | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	49	52
ARO | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	11	26
Renewable energy plan | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	9	17
Energy Waste Reduction Plan Incentive | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	34	33
Regulatory assets, noncurrent	42	34
Deferred capital spending | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	6	0
Other | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	2	0
Regulatory assets, noncurrent	7	9
Postretirement benefits | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	1,231	1,130
Costs of coal-fueled electric generating units to be retired | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	678	667
Securitized costs | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	221	247
ARO | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	216	191
Manufactured Gas Plant | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	120	130
Unamortized Loss On Reacquired Debt | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	108	70
Energy Waste Reduction Plan | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	16	10
Demand response program | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	10	1
COVID-19 costs accounting deferral | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	$ 4	$ 0