Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents	$ 187	$ 161
Restricted cash and cash equivalents	28	27
Accounts receivable and accrued revenue, less allowances	670	869
Notes receivable	40	49
Accounts receivable - related parties	10	10
Inventories at average cost
Gas in underground storage	760	929
Materials and supplies	96	92
Generating plant fuel stock	196	166
Deferred income taxes		24
Deferred property taxes	136	187
Regulatory assets	13	1
Prepayments and other current assets	70	50
Total current assets	2,206	2,565
Plant, Property, and Equipment
Plant, property, and equipment, gross	14,959	14,751
Less accumulated depreciation and amortization	4,973	4,901
Plant, property, and equipment, net	9,986	9,850
Construction work in progress	1,011	783
Total plant, property, and equipment	10,997	10,633
Other Non-current Assets
Regulatory assets, noncurrent	2,335	2,466
Accounts and notes receivable, less allowances	461	462
Investments	54	50
Other	240	276
Total other non-current assets	3,090	3,254
Total Assets	16,293	16,452
Liabilities and Equity
Current portion of long-term debt, capital and finance lease obligations	653	1,057
Accounts payable	527	575
Accounts payable - related parties	9	9
Accrued rate refunds	37	30
Accrued interest	96	101
Accrued taxes	199	282
Deferred income taxes	28
Regulatory Liability, Current	122	125
Other current liabilities	136	159
Total current liabilities	1,807	2,338
Non-current Liabilities
Long-term debt	6,221	6,040
Non-current portion of capital and finance lease obligations	157	167
Regulatory liabilities	1,933	1,875
Postretirement benefits	1,289	1,289
Asset retirement obligations	261	254
Deferred investment tax credit	44	46
Deferred income taxes	1,090	1,035
Other non-current liabilities	336	336
Total non-current liabilities	11,331	11,042
Commitments and Contingencies (Notes 3, 4, 5, 7, and 8)
Equity
Common stock	3	3
Other paid-in capital	4,664	4,627
Accumulated other comprehensive loss	(45)	(49)
Retained earnings (Accumulated deficit)	(1,511)	(1,553)
Total common stockholders equity	3,111	3,028
Noncontrolling interests	44	44
Total equity	3,155	3,072
Total Liabilities and Equity	16,293	16,452
Consumers Energy Company [Member]
Assets
Cash and cash equivalents	154	85
Restricted cash and cash equivalents	27	26
Accounts receivable and accrued revenue, less allowances	659	860
Notes receivable	13	23
Accounts receivable - related parties	1	1
Accrued power supply revenue		0
Inventories at average cost
Gas in underground storage	756	929
Materials and supplies	92	88
Generating plant fuel stock	196	164
Deferred property taxes	136	187
Regulatory assets	13	1
Prepayments and other current assets	63	43
Total current assets	2,110	2,407
Plant, Property, and Equipment
Plant, property, and equipment, gross	14,825	14,621
Less accumulated depreciation and amortization	4,915	4,846
Plant, property, and equipment, net	9,910	9,775
Construction work in progress	1,010	782
Total plant, property, and equipment	10,920	10,557
Other Non-current Assets
Regulatory assets, noncurrent	2,335	2,466
Accounts and notes receivable, less allowances	1	1
Investments	31	35
Other	157	196
Total other non-current assets	2,524	2,698
Total Assets	15,554	15,662
Liabilities and Equity
Current portion of long-term debt, capital and finance lease obligations	62	363
Accounts payable	512	561
Accounts payable - related parties	12	11
Accrued rate refunds	37	30
Accrued interest	65	73
Accrued taxes	271	287
Deferred income taxes	85	73
Regulatory Liability, Current	122	125
Other current liabilities	108	119
Total current liabilities	1,274	1,642
Non-current Liabilities
Long-term debt	3,967	3,987
Non-current portion of capital and finance lease obligations	157	167
Regulatory liabilities	1,933	1,875
Postretirement benefits	1,227	1,225
Asset retirement obligations	260	253
Deferred investment tax credit	44	46
Deferred income taxes	1,846	1,817
Other non-current liabilities	262	256
Total non-current liabilities	9,696	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	(1)	(2)
Retained earnings (Accumulated deficit)	593	554
Total common stockholders equity	4,540	4,350
Preferred stock	44	44
Total equity	4,584	4,394
Total Liabilities and Equity	$ 15,554	$ 15,662