Consolidated Statements Of Changes In Equity (USD $)
In Millions
Consumers Energy Company [Member]
CMS Energy Common Stock [Member]
Consumers Energy Company [Member]
Other Paid-in Capital [Member]
Consumers Energy Company [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
Consumers Energy Company [Member]
Retirement benefits liability [Member]
Consumers Energy Company [Member]
Investments [Member]
Consumers Energy Company [Member]
Retained Earnings (Accumulated Deficit) [Member]
Consumers Energy Company [Member]
Preferred Stock [Member]
Consumers Energy Company [Member]
CMS Energy Common Stock [Member]
Other Paid-in Capital [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
Retirement benefits liability [Member]
Investments [Member]
Derivative instruments [Member]
Retained Earnings (Accumulated Deficit) [Member]
Noncontrolling Interest [Member]
Total
Total Equity, beginning at Jun. 30, 2011 $ 841 $ 2,957   $ (15) $ 15 $ 511 $ 44 $ 4,353 $ 3 $ 4,621 $ (38) $ (38) $ 1 $ (1) $ (1,628) $ 44 $ 3,002
Common stock issued                    7              
Common stock reissued                                   
Common stock repurchased                   (6)              
Stockholder contribution                                   
Retirement benefits liability adjustments, net of tax                                    
Unrealized gain (loss) on investments, net of tax                          (2)       (2)
Net income           155   155                 140
Net income attributable to CMS Energy                             139   139
Common stock dividends declared           (96)                 (53)    
Preferred stock dividends declared           (1)                      
Income attributable to noncontrolling interests                               1 1
Distributions and other changes in noncontrolling interests                               (1)  
Total Equity, end at Sep. 30, 2011 841 2,957    (15) 15 569 44 4,411 3 4,622 (40) (38) (1) (1) (1,542) 44 3,087
Total Equity, beginning at Dec. 31, 2010 841 2,832   (16) 16 463 44 4,180 2 4,588 (40) (39)   (1) (1,757) 44 2,837
Common stock issued                 1 35              
Common stock reissued                   5              
Common stock repurchased                   (6)              
Stockholder contribution   125           125                  
Retirement benefits liability adjustments, net of tax       1       1       1         1
Unrealized gain (loss) on investments, net of tax         (1)     (1)         (1)       (1)
Net income           400   400                 376
Net income attributable to CMS Energy                             374   374
Common stock dividends declared           (292)                 (159)    
Preferred stock dividends declared           (2)                      
Income attributable to noncontrolling interests                               2 2
Distributions and other changes in noncontrolling interests                               (2)  
Total Equity, end at Sep. 30, 2011 841 2,957    (15) 15 569 44 4,411 3 4,622 (40) (38) (1) (1) (1,542) 44 3,087
Total Equity, beginning at Dec. 31, 2011 841 2,957 (2) (19) 17 554 44 4,394 3 4,627 (49) (48)   (1) (1,553) 44 3,072
Common stock issued                    38              
Common stock reissued                   6              
Common stock repurchased                   (9)              
Stockholder contribution   150           150                  
Retirement benefits liability adjustments, net of tax       2       2       3         3
Unrealized gain (loss) on investments, net of tax                          3       3
Net income           361   361                 317
Net income attributable to CMS Energy                             315   315
Common stock dividends declared           (302)                 (188)    
Preferred stock dividends declared           (2)                      
Income attributable to noncontrolling interests                               2 2
Distributions and other changes in noncontrolling interests                               (2)  
Total Equity, end at Sep. 30, 2012 841 3,107    (17) 17 611 44 4,603 3 4,662 (43) (45) 3 (1) (1,426) 44 3,240
Total Equity, beginning at Jun. 30, 2012 841 3,107 (1) (18) 17 593 44 4,584 3 4,664 (45) (46) 2 (1) (1,511) 44 3,155
Common stock issued                    7              
Common stock reissued                                   
Common stock repurchased                   (9)              
Stockholder contribution                                   
Retirement benefits liability adjustments, net of tax       1       1       1         1
Unrealized gain (loss) on investments, net of tax                          1       1
Net income           163   163                 149
Net income attributable to CMS Energy                             148   148
Common stock dividends declared           (144)                 (63)    
Preferred stock dividends declared           (1)                      
Income attributable to noncontrolling interests                               1 1
Distributions and other changes in noncontrolling interests                               (1)  
Total Equity, end at Sep. 30, 2012 $ 841 $ 3,107    $ (17) $ 17 $ 611 $ 44 $ 4,603 $ 3 $ 4,662 $ (43) $ (45) $ 3 $ (1) $ (1,426) $ 44 $ 3,240