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Contingencies And Commitments (Contingencies And Commitments) (Details)
violation in Thousands
1 Months Ended 6 Months Ended
Jun. 30, 2019
USD ($)
violation
site
Jan. 31, 2019
USD ($)
Jun. 30, 2019
USD ($)
site
lawsuit
Dec. 31, 2018
USD ($)
Loss Contingencies [Line Items]        
Regulatory assets $ 2,344,000,000   $ 2,344,000,000 $ 1,743,000,000
Consumers Energy Company        
Loss Contingencies [Line Items]        
Regulatory assets 2,344,000,000   2,344,000,000 $ 1,743,000,000
Bay Harbor        
Loss Contingencies [Line Items]        
Accrual for obligations for environmental remediation $ 45,000,000   $ 45,000,000  
Discounted projected costs rate 4.34%   4.34%  
Remaining undiscounted obligation amount $ 56,000,000   $ 56,000,000  
Accrual for environmental loss contingencies, inflation rate 1.00%   1.00%  
Electric Utility | NREPA | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for obligations for environmental remediation $ 3,000,000   $ 3,000,000  
Electric Utility | NREPA | Minimum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs 3,000,000   3,000,000  
Electric Utility | NREPA | Maximum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs 4,000,000   4,000,000  
Electric Utility | CERCLA Liability | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for obligations for environmental remediation 3,000,000   3,000,000  
Electric Utility | CERCLA Liability | Minimum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs 3,000,000   3,000,000  
Electric Utility | CERCLA Liability | Maximum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Remediation and other response activity costs 8,000,000   8,000,000  
Gas Utility | NREPA | Maximum | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for obligations for environmental remediation 1,000,000   1,000,000  
Remediation and other response activity costs 3,000,000   3,000,000  
Gas Utility | Manufactured Gas Plant | Consumers Energy Company        
Loss Contingencies [Line Items]        
Accrual for obligations for environmental remediation $ 68,000,000   $ 68,000,000  
Discounted projected costs rate 2.57%   2.57%  
Remaining undiscounted obligation amount $ 74,000,000   $ 74,000,000  
Number of former MGPs | site 23   23  
Accrual for environmental loss contingencies, inflation rate 2.50%   2.50%  
Authorized recovery, collection period     10 years  
Regulatory assets $ 129,000,000   $ 129,000,000  
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   $ 10,000,000  
MPSC Gas Staking MISS DIG Act [Member] | Consumers Energy Company        
Loss Contingencies [Line Items]        
Number of alleged violations | violation 20      
Maximum possible loss per violation $ 5,000