Regulatory Matters (Narrative) (Details) (USD $) In Millions, unless otherwise specified																			1 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Consumers Energy Company [Member]	Dec. 31, 2011 Consumers Energy Company [Member]	Oct. 31, 2011 Consumers Energy Company [Member]	Mar. 31, 2012 2011 Electric Rate Case [Member] Consumers Energy Company [Member]	Dec. 31, 2011 2011 Electric Rate Case [Member] Consumers Energy Company [Member]	Nov. 30, 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]	Sep. 30, 2011 2010-2011 Gas Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Mar. 31, 2012 Gas Revenue Decoupling Mechanism [Member] Consumers Energy Company [Member]	Mar. 31, 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]	Mar. 31, 2012 DOE Settlement [Member] Consumers Energy Company [Member]	Jul. 31, 2011 Nuclear Fuel Disposal Cost [Member] Consumers Energy Company [Member]
Annual Rate Increase Requested by Consumers									$ 195
Requested Recovery										27	32		16
Write-Off of Regulatory Asset												59
Regulatory assets, noncurrent	2,362	2,466	2,362	2,466										28	85
Amount Paid to Transfer Ownership and Responsibility															30
Regulatory liabilities	120	125	120	125														120
Proposed 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
Proposed Annual Amount Of Reduction Of Renewable Energy Plan Surcharge Billed To Customers					3
Energy Optimization Incentive to be Requested for Exceeding 2011 Savings Targets			15
Rate of Return on Equity Requested by Consumers									10.70%
Annual Rate Increase Recommended						43
Rate Of Return On Equity Recommended						10.25%
Annual Rate Increase Self-Implemented by Consumers							118
Amount Of Proposed Self-implemented Rate Increase								147
Amount Of Self-Implemented Rate Increase Authorized By the MPSC							$ 118