Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	$ 2,485		$ 2,485		$ 2,489
Regulatory liabilities	84		84		87
Revenue	1,443	$ 1,445	3,307	$ 3,504
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	2,485		2,485		2,489
Regulatory liabilities	84		84		87
Revenue	1,330	$ 1,334	3,074	$ 3,277
Gain Shared with Customers for Substation Transmission Assets to METC | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory liabilities	15		15		17
Energy Waste Reduction Plan Incentive | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Requested recovery collection	34		34
Revenue					$ 34
COVID-19 Costs Accounting Deferral | Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets, noncurrent	$ 9		$ 9