Contingencies And Commitments (Contingencies And Commitments) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) item lawsuit	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Regulatory assets	$ 1,827	$ 1,840
Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Regulatory assets	$ 1,827	$ 1,840
Bay Harbor [Member]
Loss Contingencies [Line Items]
Environmental remediation permit renewal term	5 years
Demand for payment by USEPA	$ 8
Accrual for environmental loss contingencies	$ 54
Discounted projected costs rate	4.34%
Remaining undiscounted obligation amount	$ 69
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
Remediation and other response activity costs, minimum	3
Remediation and other response activity costs, maximum	8
Manufactured Gas Plant [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 114
Discounted projected costs rate	2.57%
Remaining undiscounted obligation amount	$ 130
Number of former MGPs | item	23
Regulatory assets	$ 145
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
Remediation and other response activity costs, minimum	3
Remediation and other response activity costs, maximum	5
Gas Utility [Member] | NREPA [Member] | Consumers Energy Company [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	1
Remediation and other response activity costs, maximum	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
Individual Lawsuits [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	1