Regulatory Matters (Narrative) (Details) (USD $)			6 Months Ended			12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Power Supply Cost Recover (PSCR) [Member] Consumers Energy Company [Member] Authorized by MPSC [Member]	Jun. 30, 2011 Electric Rate Case [Member] Consumers Energy Company [Member]	Dec. 31, 2010 Electric Rate Case [Member] Consumers Energy Company [Member]	Dec. 31, 2010 Power Supply Cost Recover (PSCR) [Member] Consumers Energy Company [Member]	Mar. 31, 2011 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member]	Mar. 31, 2010 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Electric Decoupling [Member]	Mar. 31, 2011 Consumers Energy Company [Member] Electric Decoupling [Member]	Mar. 31, 2011 Consumers Energy Company [Member] Uncollectible Expense Tracking Mechanism [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Electric Operation and Maintenance Show-Cause Order [Member]	Dec. 31, 2009 Consumers Energy Company [Member] Electric Operation and Maintenance Show-Cause Order [Member]	May 31, 2011 Gas Rate Case [Member] Consumers Energy Company [Member]	Feb. 28, 2011 Gas Rate Case [Member] Consumers Energy Company [Member]	Jan. 31, 2011 Gas Rate Case [Member] Consumers Energy Company [Member]	Aug. 31, 2010 Gas Rate Case [Member] Consumers Energy Company [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Big Rock [Member]	Apr. 30, 2010 Consumers Energy Company [Member] Big Rock [Member]	Feb. 28, 2010 Consumers Energy Company [Member] Big Rock [Member]	Jun. 30, 2011 Consumers Energy Company [Member] Electric Plant [Member]	Feb. 28, 2010 Consumers Energy Company [Member] Electric Plant [Member]	Feb. 28, 2010 Consumers Energy Company [Member] Consumers Share of Ludington [Member]	Jun. 30, 2011 Consumers Energy Company [Member]	May 31, 2011 Consumers Energy Company [Member]	Apr. 30, 2011 Consumers Energy Company [Member]	Dec. 31, 2010 Consumers Energy Company [Member]
Annual Rate Increase Authorized by MPSC					$ 146,000,000									$ 31,000,000
Annual Rate Increase Requested by Consumers				195,000,000													55,000,000
Difference Between the Annual Rate Increase Authorized by MPSC and the Annual Rate Increase Self-implemented by Consumers					4,000,000
Amount of rates to be refunded to customers				0
Requested Recovery										27,000,000	3,000,000
Regulatory assets	2,050,000,000	2,093,000,000							58,000,000									85,000,000						2,050,000,000			2,093,000,000
Percentage of Difference Between Rate Base Expense and Actual Expense To Collect/Refund											80.00%
Difference Between the Operation and Maintenance Expenditures Ordered by MPSC and the Operation and Maintenance Expenditures Incurred by Consumers During 2007													14,000,000
Imposed fine by MPSC												65,200
Contribution To Fund Decommissioning Costs Previously Collected																				44,000,000
Revenue Collected in Excess of Costs to Decommission Big Rock, Plus Interest, and Ordered for Refund																			85,000,000
Amount Paid to Transfer Ownership and Responsibility																		30,000,000
Nuclear Fuel Storage Costs Incurred as a Result of the DOE's Failure to Accept Spent Nuclear Fuel																		55,000,000
Recommended Renewable Recovery Disallowance																								3,000,000
Annual Amount Of Reduction Of Renewable Energy Plan Surcharge Billed To Customers																									54,000,000
Authorized Energy Optimization Incentive for Exceeding 2009 Savings Targets																									6,000,000
Requested Energy Optimization Incentive for Exceeding 2010 Savings Targets																										8,000,000
Requested Increase In Annual Depreciation Expense																						46,000,000	9,000,000
Authorized increase in depreciation expense																					19,000,000
Rate of Return on Equity Requested				10.70%													11.00%
Rate of Return On Equity Authorized by Public Service Commission														10.50%
Net Over/(Under) Recovery, Including Interest			(31,000,000)			(15,000,000)	6,000,000	1,000,000
Amount Of Proposed Self-implemented Rate Increase																48,000,000
Revised Amount Of Proposed Self-implemented Rate Increase															$ 29,000,000