Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Assets
Cash and cash equivalents	$ 93		$ 161
Restricted cash and cash equivalents	29		27
Accounts receivable and accrued revenue, less allowances	855		869
Notes receivable	41		49
Accounts receivable - related parties	10		10
Accrued power supply revenue	32
Inventories at average cost
Gas in underground storage	820		929
Materials and supplies	96		92
Generating plant fuel stock	168		166
Deferred income taxes			24
Deferred property taxes	190		187
Regulatory assets	35		1
Prepayments and other current assets	53		50
Total current assets	2,422		2,565
Plant, Property, and Equipment
Plant, property, and equipment, gross	15,592		14,751
Less accumulated depreciation and amortization	5,121		4,901
Plant, property, and equipment, net	10,471		9,850
Construction work in progress	1,080		783
Total plant, property, and equipment	11,551	[1]	10,633	[1]
Other Non-current Assets
Regulatory assets, noncurrent	2,287		2,466
Accounts and notes receivable	521		462
Investments	57		50
Other	293		276
Total other non-current assets	3,158		3,254
Total Assets	17,131		16,452
Liabilities and Equity
Current portion of long-term debt, capital and finance lease obligations	541		1,057
Notes payable	110
Accounts payable	512		575
Accounts payable - related parties	9		9
Accrued rate refunds	6		30
Accrued interest	95		101
Accrued taxes	279		282
Deferred income taxes	68
Regulatory liabilities, current	25		125
Other current liabilities	152		159
Total current liabilities	1,797		2,338
Non-current Liabilities
Long-term debt	6,710		6,040
Non-current portion of capital and finance lease obligations	153		167
Regulatory liabilities	2,101		1,875
Postretirement benefits	1,451		1,289
Asset retirement obligations	312		254
Deferred investment tax credit	43		46
Deferred income taxes	1,015		1,035
Other non-current liabilities	311		336
Total non-current liabilities	12,096		11,042
Commitments and Contingencies (Notes 3, 4, 5, and 7)
Equity
Common stock	3		3
Other paid-in capital	4,669		4,627
Accumulated other comprehensive loss	(55)		(49)
Retained earnings (Accumulated deficit)	(1,423)		(1,553)
Total common stockholders equity	3,194		3,028
Noncontrolling interests	44		44
Total equity	3,238		3,072
Total Liabilities and Equity	17,131		16,452
Consumers Energy Company [Member]
Assets
Cash and cash equivalents	5		85
Restricted cash and cash equivalents	28		26
Accounts receivable and accrued revenue, less allowances	844		860
Notes receivable			23
Accounts receivable - related parties	1		1
Accrued power supply revenue	32
Inventories at average cost
Gas in underground storage	816		929
Materials and supplies	92		88
Generating plant fuel stock	167		164
Deferred property taxes	190		187
Regulatory assets	35		1
Prepayments and other current assets	45		43
Total current assets	2,255		2,407
Plant, Property, and Equipment
Plant, property, and equipment, gross	15,456		14,621
Less accumulated depreciation and amortization	5,061		4,846
Plant, property, and equipment, net	10,395		9,775
Construction work in progress	1,080		782
Total plant, property, and equipment	11,475	[1]	10,557	[1]
Other Non-current Assets
Regulatory assets, noncurrent	2,287		2,466
Accounts and notes receivable	17		1
Investments	32		35
Other	209		196
Total other non-current assets	2,545		2,698
Total Assets	16,275		15,662
Liabilities and Equity
Current portion of long-term debt, capital and finance lease obligations	63		363
Notes payable	110
Accounts payable	501		561
Accounts payable - related parties	11		11
Accrued rate refunds	6		30
Accrued interest	65		73
Accrued taxes	376		287
Deferred income taxes	144		73
Regulatory liabilities, current	25		125
Other current liabilities	109		119
Total current liabilities	1,410		1,642
Non-current Liabilities
Long-term debt	4,297		3,987
Non-current portion of capital and finance lease obligations	153		167
Regulatory liabilities	2,101		1,875
Postretirement benefits	1,385		1,225
Asset retirement obligations	311		253
Deferred investment tax credit	43		46
Deferred income taxes	1,741		1,817
Other non-current liabilities	252		256
Total non-current liabilities	10,283		9,626
Commitments and Contingencies (Notes 3, 4, 5, and 7)
Equity
Common stock	841		841
Other paid-in capital	3,107		2,957
Accumulated other comprehensive loss	(8)		(2)
Retained earnings (Accumulated deficit)	598		554
Total common stockholders equity	4,538		4,350
Preferred stock	44		44
Total equity	4,582		4,394
Total Liabilities and Equity	$ 16,275		$ 15,662

[1] For the year ended December 31, 2012, utility plant additions were $999 million and utility plant retirements were $168 million. For the year ended December 31, 2011, utility plant additions were $700 million and utility plant retirements were $104 million.