Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	$ 33		$ 37
Regulatory assets, noncurrent	2,489		1,743
Regulatory liabilities, current	87		155
Regulatory liability, noncurrent	3,742		3,681
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	33		37
Regulatory assets, noncurrent	2,489		1,743
Total regulatory assets	2,522		1,780
Regulatory liabilities, current	87		155
Regulatory liability, noncurrent	3,742		3,681
Total regulatory liabilities	3,829		3,836
Income taxes, net | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	65		18
Regulatory liability, noncurrent	1,510		1,537
Gain shared with customers | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	17		0
Reserve for customer refunds | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	2		36
TCJA reserve for refund | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	0		98
Regulatory liability, noncurrent	0	$ 62	35
Other | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities, current	3		3
Regulatory liability, noncurrent	11		9
Cost of removal | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	2,126		1,966
Renewable energy grant | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	52		54
ARO | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	26		38
Renewable energy plan | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liability, noncurrent	17		42
Energy Waste Reduction Plan Incentive | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	33		32
Regulatory assets, noncurrent	34		34
Other | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current	0		5
Regulatory assets, noncurrent	4		2
Postretirement benefits | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	1,130		1,028
Costs of coal-fueled electric generating units to be retired | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	667		0
Securitized Costs | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	247		273
ARO | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	191		175
Manufactured Gas Plant | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent			133
Unamortized Loss On Reacquired Debt | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	70		68
Deferred capital spending | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	3		0
Gas Storage Inventory Adjustments | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	3		4
Energy Waste Reduction Plan | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	$ 10		$ 26