Consolidated Statements Of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating Revenue	$ 1,979	$ 1,743
Operating Expenses
Fuel for electric generation	154	130
Purchased and interchange power	333	317
Purchased power - related parties	23	22
Cost of gas sold	607	550
Maintenance and other operating expenses	282	295
Depreciation and amortization	181	172
General taxes	70	69
Total operating expenses	1,650	1,555
Operating Income	329	188
Other Income (Expense)
Interest income		1
Allowance for equity funds used during construction	3	2
Income from equity method investees	5	5
Other income	3	3
Other expense	(3)	(2)
Total other income	8	9
Interest Charges
Interest on long-term debt	94	94
Other interest expense	5	6
Allowance for borrowed funds used during construction	(1)	(1)
Total interest charges	98	99
Income Before Income Taxes	239	98
Income Tax Expense	95	38
Income From Continuing Operations	144	60
Income From Discontinued Operations		7
Net Income	144	67
Net Income Attributable to Common Stockholders
Amounts attributable to continuing operations	144	60
Amounts attributable to discontinued operations		7
Net Income Available to Common Stockholders	144	67
Basic Earnings Per Average Common Share
Basic earnings from continuing operations	$ 0.55	$ 0.23
Basic earnings from discontinued operations		$ 0.03
Basic earnings attributable to common stock	$ 0.55	$ 0.26
Diluted Earnings Per Average Common Share
Diluted earnings from continuing operations	$ 0.53	$ 0.22
Diluted earnings from discontinued operations		$ 0.03
Diluted earnings attributable to common stock	$ 0.53	$ 0.25
Dividends Declared Per Common Share	$ 0.255	$ 0.24
Consumers Energy Company [Member]
Operating Revenue	1,919	1,675
Operating Expenses
Fuel for electric generation	133	106
Purchased and interchange power	329	313
Purchased power - related parties	23	21
Cost of gas sold	600	536
Maintenance and other operating expenses	266	277
Depreciation and amortization	180	171
General taxes	69	68
Total operating expenses	1,600	1,492
Operating Income	319	183
Other Income (Expense)
Interest income		1
Allowance for equity funds used during construction	3	2
Other income	7	8
Other expense	(3)	(2)
Total other income	7	9
Interest Charges
Interest on long-term debt	59	61
Other interest expense	3	4
Allowance for borrowed funds used during construction	(1)	(1)
Total interest charges	61	64
Income Before Income Taxes	265	128
Income Tax Expense	103	52
Net Income	162	76
Net Income Attributable to Common Stockholders
Net Income Available to Common Stockholders	$ 162	$ 76