Plant, Property, and Equipment (Property, Plant and Equipment Table) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Construction work in progress	$ 783		$ 570
Accumulated Depreciation and Amortization	4,901		4,646
Public Utilities, Property, Plant and Equipment, Net	10,633	[1]	10,069	[1]
Public Utilities, Property Plant and Equipment Additions	700		783
Public Utilities, Property Plant and Equipment Disposals	104		85
Consumers Energy Company [Member]
Capital Leased Assets, Gross	280		278		306
Construction work in progress	782		566
Accumulated Depreciation and Amortization	4,846		4,593
Public Utilities, Property, Plant and Equipment, Net	10,557	[1]	9,995	[1]
Public Utilities, Property Plant and Equipment Additions	700		783
Public Utilities, Property Plant and Equipment Disposals	104		85
Electricity Generation Plant, Non-Nuclear [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	18
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	85
Public Utilities, Property, Plant and Equipment, Generation or Processing	3,936		3,812
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	18
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	85
Public Utilities, Property, Plant and Equipment, Generation or Processing	3,936		3,812
Electric Distribution [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	12
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	75
Public Utilities, Property, Plant and Equipment, Distribution	5,538		5,250
Electric Distribution [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	12
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	75
Public Utilities, Property, Plant and Equipment, Distribution	5,538		5,250
Electric Other [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	7
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	40
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	651		609
Electric Other [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	7
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	40
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	651		609
Electric Capital Leases [Member]
Capital Leased Assets, Gross	275		273
Electric Capital Leases [Member] | Consumers Energy Company [Member]
Capital Leased Assets, Gross	275		273
Gas Underground Storage Facilities [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	30
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	65
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	322	[2]	311	[2]
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	30
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	65
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	322	[2]	311	[2]
Gas Transmission [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	13
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	75
Public Utilities, Property, Plant and Equipment, Transmission	722		713
Gas Transmission [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	13
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	75
Public Utilities, Property, Plant and Equipment, Transmission	722		713
Gas Distribution [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	30
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	80
Public Utilities, Property, Plant and Equipment, Distribution	2,754		2,654
Gas Distribution [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	30
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	80
Public Utilities, Property, Plant and Equipment, Distribution	2,754		2,654
Gas Other [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	5
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	50
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	403		380
Gas Other [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	5
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	50
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	403		380
Gas Capital Leases [Member]
Capital Leased Assets, Gross	5		5
Gas Capital Leases [Member] | Consumers Energy Company [Member]
Capital Leased Assets, Gross	5		5
Enterprises IPP [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	3
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	30
Plant, Property, and Equipment, at cost	89		85
Plant, Property, and Equipment, Gross	89		85
Enterprises Other [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	3
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	40
Plant, Property, and Equipment, at cost	20		17
Plant, Property, and Equipment, Gross	20		17
Other [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	1
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	51
Public Utilities, Property Plant and Equipment, Gross	36		36
Other [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	8
Public Utilities, Property, Plant and Equipment, Useful Life, Maximum	51
Unregulated Operation [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Useful Life, Minimum	1
Other non-utility property	15		15
Base Natural Gas [Member] | Gas Underground Storage Facilities [Member]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	26		26
Base Natural Gas [Member] | Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member]
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 26		$ 26

[1] For the year ended December 31, 2011, utility plant additions were $700 million and utility plant retirements were $104 million. For the year ended December 31, 2010, utility plant additions were $783 million and utility plant retirements were $85 million.

[2] Underground storage includes base natural gas of $26 million at December 31, 2011 and 2010. Base natural gas is not subject to depreciation.