Consolidated Statements of Changes in Equity (USD $)
In Millions
Consumers Energy Company [Member]
CMS Energy Common Stock [Member]
Consumers Energy Company [Member]
Other Paid-in Capital [Member]
Consumers Energy Company [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
Consumers Energy Company [Member]
Retirement benefits liability [Member]
Consumers Energy Company [Member]
Investments [Member]
Consumers Energy Company [Member]
Retained Earnings (Accumulated Deficit) [Member]
Consumers Energy Company [Member]
Preferred Stock [Member]
Consumers Energy Company [Member]
Comprehensive Income [Member]
Consumers Energy Company [Member]
CMS Energy Common Stock [Member]
Other Paid-in Capital [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
Retirement benefits liability [Member]
Investments [Member]
Derivative instruments [Member]
Retained Earnings (Accumulated Deficit) [Member]
Preferred Stock [Member]
Noncontrolling Interest [Member]
Comprehensive Income [Member]
Total
Total Equity, beginning at Jun. 30, 2010$ 841$ 2,832$ (1)$ (11)$ 11$ 415$ 44 $ 4,132$ 2$ 4,569$ (32)$ (30)$ 0$ (1)$ (1,831)$ 239$ 45 $ 2,941
Common stock issued          5         
Common stock reissued, value          0         
Common stock repurchased          (1)         
Charge for deferred issuance costs          8    (8)    
Stockholder's contribution 0                  
Income attributable to noncontrolling interests                 111
Retirement benefits liability adjustments, net of tax       0    0     0 
Unrealized gain (loss) on investments, net of tax    6  6     0    0 
Net Income     160 160160         146146
Common stock dividends declared     (91)         (34)    
Preferred stock dividends declared     (1)         (3)    
Distributions and other changes in noncontrolling interests                 (1)  
Net Income Attributable to CMS Energy               145  145145
Total Comprehensive Income       166          145 
Conversion of preferred stock                (239)   
Total Equity, end at Sep. 30, 20108412,8326(11)1748344 4,20624,581(31)(30)0(1)(1,731)045 2,866
Total Equity, beginning at Dec. 31, 20098412,582(2)(11)1338944 3,85824,560(33)(32)0(1)(1,927)23997 2,938
Common stock issued          15         
Common stock reissued, value          0         
Common stock repurchased          (2)         
Charge for deferred issuance costs          8    (8)    
Stockholder's contribution 250      250           
Income attributable to noncontrolling interests                 333
Retirement benefits liability adjustments, net of tax       0    2     2 
Unrealized gain (loss) on investments, net of tax    4  4     0    0 
Net Income     355 355355         318318
Common stock dividends declared     (259)         (103)    
Preferred stock dividends declared     (2)         (8)    
Distributions and other changes in noncontrolling interests                 (55)  
Net Income Attributable to CMS Energy               315  315315
Total Comprehensive Income       359          317 
Conversion of preferred stock                (239)   
Total Equity, end at Sep. 30, 20108412,8326(11)1748344 4,20624,581(31)(30)0(1)(1,731)045 2,866
Total Equity, beginning at Dec. 31, 20108412,8320(16)1646344 4,18024,588(40)(39) (1)(1,757)044 2,837
Common stock issued         135         
Common stock reissued, value          5         
Common stock repurchased          (6)         
Charge for deferred issuance costs          0    0    
Stockholder's contribution 125      125           
Income attributable to noncontrolling interests                 222
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 400400         376376
Common stock dividends declared     (292)         (159)    
Preferred stock dividends declared     (2)         0    
Distributions and other changes in noncontrolling interests                 (2)  
Net Income Attributable to CMS Energy               374  374374
Total Comprehensive Income       400          374 
Total Equity, end at Sep. 30, 20118412,9570(15)1556944 4,41134,622(40)(38)(1)(1)(1,542)044 3,087
Total Equity, beginning at Jun. 30, 20118412,9570(15)1551144 4,35334,621(38)(38)1(1)(1,628)044 3,002
Common stock issued          7         
Common stock reissued, value          0         
Common stock repurchased          (6)         
Charge for deferred issuance costs          0    0    
Stockholder's contribution 0                  
Income attributable to noncontrolling interests                 111
Retirement benefits liability adjustments, net of tax       0    0     0 
Unrealized gain (loss) on investments, net of tax    0  0     (2)    (2) 
Net Income     155 155155         140140
Common stock dividends declared     (96)         (53)    
Preferred stock dividends declared     (1)         0    
Distributions and other changes in noncontrolling interests                 (1)  
Net Income Attributable to CMS Energy               139  139139
Total Comprehensive Income       155          137 
Total Equity, end at Sep. 30, 2011$ 841$ 2,957$ 0$ (15)$ 15$ 569$ 44 $ 4,411$ 3$ 4,622$ (40)$ (38)$ (1)$ (1)$ (1,542)$ 0$ 44 $ 3,087