Income Taxes (Significant Components Of Income Tax Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Federal			$ 1us-gaap_CurrentFederalTaxExpenseBenefit
State and Local	24	34	21
Total Current Income Tax Expense	24us-gaap_CurrentIncomeTaxExpenseBenefit	34us-gaap_CurrentIncomeTaxExpenseBenefit	22us-gaap_CurrentIncomeTaxExpenseBenefit
Federal, deferred income taxes	198	248	205
State and Local, deferred income taxes	31	23	21
Total Deferred Income Tax Expense	229us-gaap_DeferredIncomeTaxExpenseBenefit	271us-gaap_DeferredIncomeTaxExpenseBenefit	226us-gaap_DeferredIncomeTaxExpenseBenefit
Deferred income tax credit	(3)us-gaap_OtherTaxExpenseBenefit	(3)us-gaap_OtherTaxExpenseBenefit	(3)us-gaap_OtherTaxExpenseBenefit
Tax Expense	250us-gaap_IncomeTaxExpenseBenefit	302us-gaap_IncomeTaxExpenseBenefit	245us-gaap_IncomeTaxExpenseBenefit
Consumers Energy Company [Member]
Federal	8	137	110
State and Local	36	45	37
Total Current Income Tax Expense	44	182	147
Federal, deferred income taxes	236	147	134
State and Local, deferred income taxes	29	20	19
Total Deferred Income Tax Expense	265	167	153
Deferred income tax credit	(3)	(3)	(3)
Tax Expense	$ 306	$ 346	$ 297

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.