XML 53 R35.htm IDEA: XBRL DOCUMENT v3.10.0.1
Regulatory Matters (Narrative) (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Jul. 26, 2018
Jun. 30, 2018
Mar. 31, 2018
Feb. 28, 2018
Oct. 31, 2017
Sep. 30, 2017
Mar. 31, 2017
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
May 31, 2018
Public Utilities, General Disclosures [Line Items]                          
Regulatory liabilities   $ 159           $ 159   $ 159   $ 80  
Revenue               1,492 $ 1,449 3,445 $ 3,278    
Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Regulatory liabilities   159           159   159   80  
Revenue               1,395 $ 1,362 3,250 $ 3,099    
Revenue Subject to Refund - Tax Reform Rate Change | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Regulatory liabilities   88           88   88      
Electric Rate Case | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Annual rate increase requested             $ 173            
Rate of return on equity requested             10.50%            
Annual rate increase requested, amended           $ 148              
Annual rate increase self-implemented         $ 130                
Annual rate increase authorized   72 $ 66                    
Rate of return on equity authorized     10.00%                    
Electric Rate Case | Revenue Subject to Refund - Other | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Regulatory liabilities   35           $ 35   $ 35      
Gas Rate Case | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Recommended disallowance of cost recovery       $ 115                  
Gas Rate Case Tax Reform Rate Change | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Annual rate increase authorized   $ (49)                      
Energy Waste Reduction Plan | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Requested recovery/collection                         $ 31
Revenue                       $ 31  
Subsequent Event | Gas Rate Case | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Recommended disallowance of cost recovery $ 100                        
Subsequent Event | Electric Rate Case Tax Reform Rate Change | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Annual rate increase authorized (113)                        
Maximum | Subsequent Event | Gas Rate Case | Consumers Energy Company                          
Public Utilities, General Disclosures [Line Items]                          
Disallowed costs for recently completed plant $ 145