Consolidated Statements Of Income (USD $)
In Millions, except Per Share data, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Operating Revenue $ 1,445 $ 1,507 $ 4,830 $ 4,583
Operating Expenses        
Fuel for electric generation 165 190 466 446
Purchased and interchange power 383 386 1,063 1,037
Purchased power - related parties 21 23 67 65
Cost of gas sold 76 80 849 763
Maintenance and other operating expenses 285 295 871 872
Depreciation and amortization 145 138 463 440
General taxes 54 53 174 170
Gain on asset sales, net (1) (1) (1) (1)
Total operating expenses 1,128 1,164 3,952 3,792
Operating Income 317 343 878 791
Other Income (Expense)        
Interest income 1 1 3 3
Allowance for equity funds used during construction 1 2 5 6
Income from equity method investees 3 5 11 13
Other income 2 3 7 9
Other expense (7) (11) (13) (16)
Total other income (expense)     13 15
Interest Charges        
Interest on long-term debt 96 92 289 280
Other interest expense 3 5 12 16
Allowance for borrowed funds used during construction   (1) (2) (3)
Total interest charges 99 96 299 293
Income Before Income Taxes 218 247 592 513
Income Tax Expense 91 98 240 203
Income From Continuing Operations 127 149 352 310
Income From Discontinued Operations, Net       7
Net Income 127 149 352 317
Income Attributable to Noncontrolling Interests 1 1 2 2
Net Income Attributable to Common Stockholders        
Amounts attributable to continuing operations 126 148 350 308
Amounts attributable to discontinued operations       7
Net Income Available to Common Stockholders 126 148 350 315
Income Attributable to Noncontrolling Interests        
Amounts attributable to continuing operations 1 1 2 2
Amounts attributable to discontinued operations            
Income attributable to noncontrolling interests 1 1 2 2
Basic Earnings Per Average Common Share        
Basic earnings from continuing operations $ 0.48 $ 0.56 $ 1.32 $ 1.18
Basic earnings from discontinued operations       $ 0.03
Basic earnings attributable to common stock $ 0.48 $ 0.56 $ 1.32 $ 1.21
Diluted Earnings Per Average Common Share        
Diluted earnings from continuing operations $ 0.46 $ 0.55 $ 1.29 $ 1.14
Diluted earnings from discontinued operations       $ 0.03
Diluted earnings attributable to common stock $ 0.46 $ 0.55 $ 1.29 $ 1.17
Dividends Declared Per Common Share $ 0.255 $ 0.24 $ 0.765 $ 0.72
Consumers Energy Company [Member]
        
Operating Revenue 1,386 1,448 4,647 4,405
Operating Expenses        
Fuel for electric generation 148 166 406 382
Purchased and interchange power 374 379 1,043 1,019
Purchased power - related parties 21 23 67 65
Cost of gas sold 64 74 818 734
Maintenance and other operating expenses 270 284 825 827
Depreciation and amortization 143 137 459 436
General taxes 53 51 170 165
Gain on asset sales, net (1)   (1)  
Total operating expenses 1,072 1,114 3,787 3,628
Operating Income 314 334 860 777
Other Income (Expense)        
Interest income     2 2
Interest and dividend income - related parties 1 1 1 1
Allowance for equity funds used during construction 1 2 5 6
Other income 2 3 11 14
Other expense (3) (11) (9) (16)
Total other income (expense) 1 (5) 10 7
Interest Charges        
Interest on long-term debt 58 56 177 175
Other interest expense 2 4 8 12
Allowance for borrowed funds used during construction   (1) (2) (3)
Total interest charges 60 59 183 184
Income Before Income Taxes 255 270 687 600
Income Tax Expense 102 107 272 239
Net Income 153 163 415 361
Preferred Stock Dividends and Distribution 1 1 2 2
Net Income Attributable to Common Stockholders        
Net Income Available to Common Stockholders $ 152 $ 162 $ 413 $ 359