Contingencies And Commitments (Contingencies And Commitments) (Details) $ in Millions		1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Mar. 31, 2020 USD ($) site lawsuit	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) lawsuit
Loss Contingencies [Line Items]
Regulatory assets			$ 2,465		$ 2,489
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			2,465		$ 2,489
Cost of gas sold			270	$ 401
Bay Harbor
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			$ 46
Discounted projected costs rate			4.34%
Accrual for environmental loss contingencies, inflation rate			1.00%
Remaining undiscounted obligation amount			$ 57
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			3
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			4
Electric Utility | CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			3
Electric Utility | CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3
Electric Utility | CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			8
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			1
Remediation and other response activity costs			3
Gas Utility | Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			$ 67
Discounted projected costs rate			2.57%
Accrual for environmental loss contingencies, inflation rate			2.50%
Remaining undiscounted obligation amount			$ 72
Number of former MGPs | site			23
Authorized recovery, collection period			10 years
Regulatory assets			$ 128
Equatorial Guinea Tax Claim
Loss Contingencies [Line Items]
Foreign government tax claim on sale			$ 152
Class Action Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			4
Individual Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			1
Gas Index Price Reporting Litigation
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit					2
Estimated litigation liability					$ 30
MCV PPA | Consumers Energy Company
Loss Contingencies [Line Items]
Foreign government tax claim on sale		$ 270
Underwater cables Straits of Mackinac | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Asset retirement obligation			$ 5
Ray Compressor Station | Consumers Energy Company
Loss Contingencies [Line Items]
Cost of gas sold	$ 7
Capital expenditures			$ 12