Contingencies And Commitments (Contingencies And Commitments) (Details) violation in Thousands	1 Months Ended		9 Months Ended
	Jun. 30, 2019 USD ($) violation	Jan. 31, 2019 USD ($)	Sep. 30, 2019 USD ($) site lawsuit	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Regulatory assets			$ 2,367,000,000	$ 1,743,000,000
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets			2,367,000,000	$ 1,743,000,000
Bay Harbor
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			$ 44,000,000
Discounted projected costs rate			4.34%
Remaining undiscounted obligation amount			$ 56,000,000
Accrual for environmental loss contingencies, inflation rate			1.00%
Electric Utility | NREPA | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			$ 3,000,000
Electric Utility | NREPA | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000,000
Electric Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			4,000,000
Electric Utility | CERCLA Liability | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			3,000,000
Electric Utility | CERCLA Liability | Minimum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			3,000,000
Electric Utility | CERCLA Liability | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			8,000,000
Gas Utility | NREPA | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			1,000,000
Remediation and other response activity costs			3,000,000
Gas Utility | Manufactured Gas Plant | Consumers Energy Company
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation			$ 70,000,000
Discounted projected costs rate			2.57%
Remaining undiscounted obligation amount			$ 72,000,000
Number of former MGPs | site			23
Accrual for environmental loss contingencies, inflation rate			2.50%
Authorized recovery, collection period			10 years
Regulatory assets			$ 132,000,000
Equatorial Guinea Tax Claim
Loss Contingencies [Line Items]
Foreign government tax claim on sale			$ 152,000,000
Class Action Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			4
Individual Lawsuits
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			1
MCV PPA | Consumers Energy Company
Loss Contingencies [Line Items]
Foreign government tax claim on sale		$ 270,000,000
Underwater cables Straits of Mackinac | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs			$ 10,000,000
MPSC Gas Staking MISS DIG Act | Consumers Energy Company
Loss Contingencies [Line Items]
Number of alleged violations | violation	20
Maximum possible loss per violation	$ 5,000