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Regulatory Matters (Narrative) (Details)
1 Months Ended
Apr. 30, 2016
USD ($)
item
Jan. 31, 2016
USD ($)
Nov. 30, 2015
USD ($)
Jul. 31, 2015
USD ($)
Jun. 30, 2015
USD ($)
Dec. 31, 2014
USD ($)
Mar. 31, 2016
USD ($)
Feb. 29, 2016
USD ($)
Dec. 31, 2015
USD ($)
Public Utilities, General Disclosures [Line Items]                  
Regulatory liability current             $ 76,000,000   $ 82,000,000
Consumers Energy Company [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Regulatory liability current             $ 76,000,000   82,000,000
Electric Rate Case [Member] | Consumers Energy Company [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Annual rate increase requested           $ 163,000,000      
Rate of return on equity requested           10.70%      
Annual rate increase self-implemented         $ 110,000,000        
Rate of return on equity authorized     10.30%            
Temporary rate increase     $ 165,000,000            
Electric Rate Case [Member] | Consumers Energy Company [Member] | Subsequent Event [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Annual rate increase authorized $ 126,000,000                
Number of units retired | item 7                
Electric Rate Case [Member] | Self-Implemented Rate Refunds [Member] | Consumers Energy Company [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Regulatory liability current               $ 0  
Gas Rate Case [Member] | Consumers Energy Company [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Annual rate increase requested       $ 85,000,000          
Rate of return on equity requested       10.70%          
Annual rate increase self-implemented   $ 60,000,000              
Gas Rate Case [Member] | Consumers Energy Company [Member] | Subsequent Event [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Annual rate increase authorized $ 40,000,000                
Energy Optimization Plan Incentive [Member] | Consumers Energy Company [Member]                  
Public Utilities, General Disclosures [Line Items]                  
Requested recovery/collection                 $ 18,000,000