Contingencies And Commitments (Contingencies And Commitments) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) lawsuit site	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Number of lawsuits settled | lawsuit	3
Increase due to change in estimate		$ 74
Regulatory assets	$ 2,091	1,840
Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Increase due to change in estimate		74
Regulatory assets	2,091	$ 1,840
Bay Harbor [Member]
Loss Contingencies [Line Items]
Demand for payment by USEPA	8
Accrual for environmental loss contingencies	$ 51
Discounted projected costs rate	4.34%
Remaining undiscounted obligation amount	$ 65
Accrual for environmental loss contingencies, inflation rate	1.00%
CERCLA Liability [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 3
CERCLA Liability [Member] | Minimum [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Remediation and other response activity costs	3
CERCLA Liability [Member] | Maximum [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Remediation and other response activity costs	8
Manufactured Gas Plant [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 107
Discounted projected costs rate	2.57%
Remaining undiscounted obligation amount	$ 117
Number of former MGPs | site	23
Regulatory assets	$ 139
Authorized recovery, collection period	10 years
Accrual for environmental loss contingencies, inflation rate	2.50%
Electric Utility [Member] | NREPA [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 3
Electric Utility [Member] | NREPA [Member] | Minimum [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Remediation and other response activity costs	3
Electric Utility [Member] | NREPA [Member] | Maximum [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Remediation and other response activity costs	4
Gas Utility [Member] | NREPA [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	1
Gas Utility [Member] | NREPA [Member] | Maximum [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Remediation and other response activity costs	3
Equatorial Guinea Tax Claim [Member]
Loss Contingencies [Line Items]
Foreign government tax claim on sale	$ 152
Class Action Lawsuits [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	4
Number of lawsuits pending | lawsuit	2
Individual Lawsuits [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	1