Regulatory Matters (Narrative) (Details) (USD $) In Millions, unless otherwise specified			1 Months Ended	12 Months Ended			1 Months Ended															1 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2010 Consumers Energy Company [Member]	Dec. 31, 2011 Consumers Energy Company [Member]	Jun. 30, 2012 Consumers Energy Company [Member]	May 31, 2012 Consumers Energy Company [Member]	Jun. 30, 2012 2011 Electric Rate Case [Member] Consumers Energy Company [Member]	Dec. 31, 2011 2011 Electric Rate Case [Member] Consumers Energy Company [Member]	Jun. 30, 2011 2011 Electric Rate Case [Member] Consumers Energy Company [Member]	Mar. 31, 2011 2009-2010 Electric Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Mar. 31, 2012 2010-2011 Electric Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Mar. 31, 2012 Electric Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Jun. 30, 2012 2011 Gas Rate Case [Member] Consumers Energy Company [Member]	Mar. 31, 2012 2011 Gas Rate Case [Member] Consumers Energy Company [Member]	Sep. 30, 2011 2011 Gas Rate Case [Member] Consumers Energy Company [Member]	Sep. 30, 2011 2010-2011 Gas Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Jun. 30, 2012 Gas Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Jun. 30, 2012 Big Rock Decommissioning And Related Costs [Member] Consumers Energy Company [Member]	Sep. 30, 2011 Big Rock Decommissioning And Related Costs [Member] Consumers Energy Company [Member]	Apr. 30, 2010 Big Rock Decommissioning And Related Costs [Member] Consumers Energy Company [Member]	Jun. 30, 2012 DOE Settlement [Member] Consumers Energy Company [Member]	Jul. 31, 2011 Nuclear Fuel Disposal Cost [Member] Consumers Energy Company [Member]
Annual Rate Increase Authorized by the MPSC							$ 118						$ 16
Annual Rate Increase Requested by Consumers									195						49
Requested Recovery										27	32					16
Write-Off of Regulatory Asset												59
Regulatory assets, noncurrent	2,335	2,466		2,466	2,335												33	85
Regulatory asset							14
Amount Paid to Transfer Ownership and Responsibility																		30
Regulatory Liability, Current	122	125		125	122								1								120
Regulatory Liability, Noncurrent	1,933	1,875		1,875	1,933
Amended Annual Renewable Energy Plan Surcharge Billed To Customers						20
Litigation Settlement, Gross																						120
Proposed Recovery Of Regulatory Asset																			85
Proposed Refund Of Spent Nuclear Fuel Disposal Costs Collected																			23
Remaining Portion of Litigation Settlement																			12
Revenue Collected in Excess of the Costs Incurred to Decommission Big Rock, Plus Interest, and Ordered for Refund																				85
Nuclear Fuel Storage Costs Incurred as a Result of the DOE's Failure to Accept Spent Nuclear Fuel																		55
Annual Amount Of Reduction Of Renewable Energy Plan Surcharge Billed To Customers						3
Energy Optimization Incentive Requested for Exceeding 2011 Savings Targets						15
Customer Energy Optimization Savings for 2011				115
Increase in Annual Depreciation Expense Authorized by the MPSC							20
Rate of Return on Equity Requested by Consumers									10.70%						10.70%
Public Utilities, Property, Plant and Equipment, Amount of Loss (Recovery) on Plant Abandonment			22				(14)
Annual Rate Increase Self-Implemented by Consumers								$ 118						$ 23
Rate of Return On Equity Authorized by the MPSC							10.30%
Rate of Return Authorized by the MPSC													10.30%