Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Operating Revenue	$ 1,507	$ 1,464	$ 4,583	$ 4,883
Operating Expenses
Fuel for electric generation	190	199	446	504
Purchased and interchange power	386	365	1,037	968
Purchased power - related parties	23	23	65	64
Cost of gas sold	80	107	763	1,095
Maintenance and other operating expenses	295	301	872	868
Depreciation and amortization	138	120	440	404
General taxes	53	33	170	151
Gain on asset sales, net	(1)		(1)
Total operating expenses	1,164	1,148	3,792	4,054
Operating Income	343	316	791	829
Other Income (Expense)
Interest income	1	4	3	8
Allowance for equity funds used during construction	2	1	6	4
Income (loss) from equity method investees	5	4	13	10
Other income	3	3	9	12
Other expense	(11)	(3)	(16)	(8)
Total other income (expense)		9	15	26
Interest Charges
Interest on long-term debt	92	99	280	298
Other interest expense	5	6	16	18
Allowance for borrowed funds used during construction	(1)	(1)	(3)	(3)
Total interest charges	96	104	293	313
Income Before Income Taxes	247	221	513	542
Income Tax Expense	98	81	203	168
Income From Continuing Operations	149	140	310	374
Income From Discontinued Operations, Net of Tax			7	2
Net Income	149	140	317	376
Income Attributable to Noncontrolling Interests	1	1	2	2
Net Income (Loss) Attributable to Parent	148	139	315	374
Net Income Available to Common Stockholders	148	139	315	374
Net Income Attributable to Common Stockholders
Amounts attributable to continuing operations	148	139	308	372
Amounts attributable to discontinued operations			7	2
Net Income Available to Common Stockholders	148	139	315	374
Income Attributable to Noncontrolling Interests
Amounts attributable to continuing operations	1	1	2	2
Income attributable to noncontrolling interests	1	1	2	2
Basic Earnings Per Average Common Share
Basic earnings from continuing operations	$ 0.56	$ 0.55	$ 1.18	$ 1.48
Basic earnings from discontinued operations			$ 0.03	$ 0.01
Basic earnings attributable to common stock	$ 0.56	$ 0.55	$ 1.21	$ 1.49
Diluted Earnings Per Average Common Share
Diluted earnings from continuing operations	$ 0.55	$ 0.53	$ 1.14	$ 1.42
Diluted earnings from discontinued operations			$ 0.03	$ 0.01
Diluted earnings attributable to common stock	$ 0.55	$ 0.53	$ 1.17	$ 1.43
Dividends Declared Per Common Share	$ 0.24	$ 0.21	$ 0.72	$ 0.63
Consumers Energy Company [Member]
Operating Revenue	1,448	1,397	4,405	4,688
Operating Expenses
Fuel for electric generation	166	175	382	442
Purchased and interchange power	379	362	1,019	954
Purchased power - related parties	23	24	65	64
Cost of gas sold	74	88	734	1,038
Maintenance and other operating expenses	284	286	827	824
Depreciation and amortization	137	119	436	401
General taxes	51	38	165	153
Total operating expenses	1,114	1,092	3,628	3,876
Operating Income	334	305	777	812
Other Income (Expense)
Interest income		2	2	6
Interest and dividend income - related parties	1	1	1	1
Allowance for equity funds used during construction	2	1	6	4
Other income	3	3	14	16
Other expense	(11)	(3)	(16)	(8)
Total other income (expense)	(5)	4	7	19
Interest Charges
Interest on long-term debt	56	62	175	188
Other interest expense	4	5	12	14
Allowance for borrowed funds used during construction	(1)	(1)	(3)	(3)
Total interest charges	59	66	184	199
Income Before Income Taxes	270	243	600	632
Income Tax Expense	107	88	239	232
Net Income	163	155	361	400
Preferred Stock Dividends	1	1	2	2
Net Income Available to Common Stockholders	162	154	359	398
Net Income Attributable to Common Stockholders
Net Income Available to Common Stockholders	$ 162	$ 154	$ 359	$ 398