Consolidated Statements Of Changes In Equity - USD ($)
shares in Millions, $ 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 Dec. 31, 2013   $ 3,257 $ (2) $ (17) $ 15 $ 724   $ 4,857   $ 4,715 $ (22) $ (21)   $ (1) $ (1,242) $ 37 $ 3,491
Common stock issued                   52              
Common stock repurchased                   (7)              
Conversion option on convertible debt                   7              
Stockholder contribution   495                              
Return of stockholder contribution   (178)                              
Amortization of net actuarial loss (gain)       2       2       2         2
Amortization of prior service credit                       (1)         (1)
Unrealized gain (loss) on investments, net of tax         $ 2     2                  
Reclassification adjustments included in net income, net of tax                                
Reclassification adjustments included in net income                           $ 1     (1)
Net income (loss) attributable to CMS Energy                                 381
Net income           449   449             381   382
Dividends declared on common stock           (375)                 (219)    
Preferred stock dividends and distributions declared           (1)                      
Income Attributable to Noncontrolling Interests                               1 1
Distributions, redemptions, and other changes in noncontrolling interests                               (1)  
Total Equity, end at Sep. 30, 2014 $ 841 3,574 2 (15) $ 17 797 $ 37 5,251 $ 3 4,767 (20) (20)   (1,080) 37 3,707
Total Equity, beginning at Jun. 30, 2014   3,572 2 (16) 18 798   5,250   4,761 (20) (20)     (1,099) 37 3,682
Common stock issued                   7              
Common stock repurchased                   (1)              
Stockholder contribution   180                              
Return of stockholder contribution   (178)                              
Amortization of net actuarial loss (gain)       1       1       1         1
Amortization of prior service credit                       (1)         (1)
Unrealized gain (loss) on investments, net of tax         $ (1)     (1)                  
Reclassification adjustments included in net income, net of tax                                
Reclassification adjustments included in net income                                
Net income (loss) attributable to CMS Energy                                 94
Net income           119   119             94   94
Dividends declared on common stock           (120)                 (75)    
Total Equity, end at Sep. 30, 2014 841 3,574 2 (15) $ 17 797 37 5,251 3 4,767 (20) (20)   (1,080) 37 3,707
Total Equity, beginning at Dec. 31, 2014   3,574 (7) (26) 19 832   $ 5,277   4,774 (49) (48) $ (1)   (1,058) 37 $ 3,707
Beginning of period, shares at Dec. 31, 2014               84.1                 275.2
Common stock issued                   56              
Common stock repurchased                   (11)              
Common stock reissued                   10              
Stockholder contribution   150                              
Amortization of net actuarial loss (gain)       3       $ 3       4         $ 4
Amortization of prior service credit                       (1)         (1)
Unrealized gain (loss) on investments, net of tax         (2)     (2)         (3)       (3)
Reclassification adjustments included in net income, net of tax         (5)     5                  
Reclassification adjustments included in net income                                
Net income (loss) attributable to CMS Energy                                 417
Net income           459   $ 459             417   418
Dividends declared on common stock           (359)                 (240)    
Preferred stock dividends and distributions declared           (1)                      
Income Attributable to Noncontrolling Interests                               1 $ 1
Distributions, redemptions, and other changes in noncontrolling interests                               (1)  
End of period, shares at Sep. 30, 2015               84.1                 277.1
Total Equity, end at Sep. 30, 2015 841 3,724 (11) (23) 12 931 37 $ 5,522 3 4,829 (49) (45) (4) (881) 37 $ 3,939
Total Equity, beginning at Jun. 30, 2015   $ 3,724 (12) (24) $ 12 876   5,466   4,812 (48) (46) (2)   (949) 37 3,855
Common stock issued                   $ 17              
Common stock repurchased                                
Stockholder contribution                                
Amortization of net actuarial loss (gain)       1       1       2         2
Amortization of prior service credit                       (1)         (1)
Unrealized gain (loss) on investments, net of tax                         (2)       (2)
Reclassification adjustments included in net income, net of tax                                
Reclassification adjustments included in net income                                
Net income (loss) attributable to CMS Energy                                 148
Net income           160   $ 160             148   $ 148
Dividends declared on common stock           (105)                 (80)    
End of period, shares at Sep. 30, 2015               84.1                 277.1
Total Equity, end at Sep. 30, 2015 $ 841 $ 3,724 $ (11) $ (23) $ 12 $ 931 $ 37 $ 5,522 $ 3 $ 4,829 $ (49) $ (45) $ (4) $ (881) $ 37 $ 3,939