Contingencies And Commitments (Contingencies And Commitments) (Details) $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2019 USD ($)	Mar. 31, 2019 USD ($) site lawsuit	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Regulatory assets		$ 1,711	$ 1,743
Consumers Energy Company
Loss Contingencies [Line Items]
Regulatory assets		1,711	$ 1,743
Bay Harbor
Loss Contingencies [Line Items]
Accrual for obligations for environmental remediation		$ 45
Discounted projected costs rate		4.34%
Remaining undiscounted obligation amount		$ 57
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
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		$ 72
Discounted projected costs rate		2.57%
Remaining undiscounted obligation amount		$ 76
Number of former MGPs | site		23
Accrual for environmental loss contingencies, inflation rate		2.50%
Authorized recovery, collection period		10 years
Regulatory assets		$ 131
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
MCV PPA | Consumers Energy Company
Loss Contingencies [Line Items]
Foreign government tax claim on sale	$ 270
Underwater cables Straits of Mackinac | Maximum | Consumers Energy Company
Loss Contingencies [Line Items]
Remediation and other response activity costs		$ 10