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Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period $ 340 $ 325
Incurred 11 9
Settled (6) (12)
Accretion 20 $ 18
Cash flow Revisions 74
ARO Liability, end of period 439 $ 340
Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 339 324
Incurred 11 9
Settled (6) (12)
Accretion 20 $ 18
Cash flow Revisions 74
ARO Liability, end of period 438 $ 339
Gas Treating Plant and Gas Wells [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period $ 1 $ 1
Incurred  
Settled  
Accretion  
Cash flow Revisions
ARO Liability, end of period $ 1 $ 1
Coal Ash Disposal Areas [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 120 118
Settled   (3)
Accretion 6 $ 5
Cash flow Revisions 74
ARO Liability, end of period 200 $ 120
Gas Distribution Cut, Purge, Cap [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 162 154
Incurred 11 6
Settled (6) (8)
Accretion 11 $ 10
Cash flow Revisions  
ARO Liability, end of period 178 $ 162
Asbestos Abatement [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 51 49
Settled   (1)
Accretion 3 $ 3
Cash flow Revisions  
ARO Liability, end of period 54 $ 51
Wind Parks [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period $ 6 3
Incurred $ 3
Settled  
Accretion  
Cash flow Revisions
ARO Liability, end of period $ 6 $ 6