Consolidated Balance Sheets (USD $)
In Millions, unless otherwise specified
Sep. 30, 2012
Dec. 31, 2011
Assets    
Cash and cash equivalents $ 128 $ 161
Restricted cash and cash equivalents 31 27
Accounts receivable and accrued revenue, less allowances 667 869
Notes receivable 28 49
Accounts receivable - related parties 11 10
Accrued power supply revenue 15  
Inventories at average cost    
Gas in underground storage 986 929
Materials and supplies 99 92
Generating plant fuel stock 187 166
Deferred income taxes   24
Deferred property taxes 119 187
Regulatory assets 27 1
Prepayments and other current assets 62 50
Total current assets 2,360 2,565
Plant, Property, and Equipment    
Plant, property, and equipment, gross 15,103 14,751
Less accumulated depreciation and amortization 5,047 4,901
Plant, property, and equipment, net 10,056 9,850
Construction work in progress 1,134 783
Total plant, property, and equipment 11,190 10,633
Other Non-current Assets    
Regulatory assets, noncurrent 2,273 2,466
Accounts and notes receivable, less allowances 512 462
Investments 56 50
Other 217 276
Total other non-current assets 3,058 3,254
Total Assets 16,608 16,452
Liabilities and Equity    
Current portion of long-term debt, capital and finance lease obligations 510 1,057
Accounts payable 491 575
Accounts payable - related parties 9 9
Accrued rate refunds 17 30
Accrued interest 64 101
Accrued taxes 83 282
Deferred income taxes 52  
Regulatory liabilities 122 125
Other current liabilities 137 159
Total current liabilities 1,485 2,338
Non-current Liabilities    
Long-term debt 6,711 6,040
Non-current portion of capital and finance lease obligations 155 167
Regulatory liabilities 1,939 1,875
Postretirement benefits 1,291 1,289
Asset retirement obligations 264 254
Deferred investment tax credit 44 46
Deferred income taxes 1,156 1,035
Other non-current liabilities 323 336
Total non-current liabilities 11,883 11,042
Commitments and Contingencies (Notes 3, 4, 5, 7, and 8)      
Equity    
Common stock 3 3
Other paid-in capital 4,662 4,627
Accumulated other comprehensive loss (43) (49)
Retained earnings (Accumulated deficit) (1,426) (1,553)
Total common stockholders equity 3,196 3,028
Noncontrolling interests 44 44
Total equity 3,240 3,072
Total Liabilities and Equity 16,608 16,452
Consumers Energy Company [Member]
    
Assets    
Cash and cash equivalents 57 85
Restricted cash and cash equivalents 30 26
Accounts receivable and accrued revenue, less allowances 659 860
Notes receivable   23
Accounts receivable - related parties 1 1
Accrued power supply revenue 15  
Inventories at average cost    
Gas in underground storage 982 929
Materials and supplies 95 88
Generating plant fuel stock 186 164
Deferred property taxes 119 187
Regulatory assets 27 1
Prepayments and other current assets 56 43
Total current assets 2,227 2,407
Plant, Property, and Equipment    
Plant, property, and equipment, gross 14,968 14,621
Less accumulated depreciation and amortization 4,988 4,846
Plant, property, and equipment, net 9,980 9,775
Construction work in progress 1,133 782
Total plant, property, and equipment 11,113 10,557
Other Non-current Assets    
Regulatory assets, noncurrent 2,273 2,466
Accounts and notes receivable, less allowances 26 1
Investments 31 35
Other 134 196
Total other non-current assets 2,464 2,698
Total Assets 15,804 15,662
Liabilities and Equity    
Current portion of long-term debt, capital and finance lease obligations 62 363
Accounts payable 480 561
Accounts payable - related parties 11 11
Accrued rate refunds 17 30
Accrued interest 34 73
Accrued taxes 198 287
Deferred income taxes 101 73
Regulatory liabilities 122 125
Other current liabilities 105 119
Total current liabilities 1,130 1,642
Non-current Liabilities    
Long-term debt 4,308 3,987
Non-current portion of capital and finance lease obligations 155 167
Regulatory liabilities 1,939 1,875
Postretirement benefits 1,229 1,225
Asset retirement obligations 263 253
Deferred investment tax credit 44 46
Deferred income taxes 1,881 1,817
Other non-current liabilities 252 256
Total non-current liabilities 10,071 9,626
Commitments and Contingencies (Notes 3, 4, 5, 7, and 8)      
Equity    
Common stock 841 841
Other paid-in capital 3,107 2,957
Accumulated other comprehensive loss   (2)
Retained earnings (Accumulated deficit) 611 554
Total common stockholders equity 4,559 4,350
Preferred stock 44 44
Total equity 4,603 4,394
Total Liabilities and Equity $ 15,804 $ 15,662