Contingencies And Commitments (Guarantees) (Details) $ in Millions		1 Months Ended	12 Months Ended
		Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) $ / MWh MW	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Guarantees And Other Contingencies [Line Items]
PPE reduction resulting from tax refund			$ 34
Income Tax Settlement [Member]
Guarantees And Other Contingencies [Line Items]
Reduction of income tax expense			3
General Taxes [Member]
Guarantees And Other Contingencies [Line Items]
Reduction of income tax expense			$ 3
Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Expiration Date	[1]		Indefinite
Maximum obligation	[1]		$ 30
Consumers Energy Company [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund		$ 60		$ 37
Tax refund received		13
Note receivable in 2017		30
Note receivable, in 2018		17
Gain (loss) related to tax settlement			$ 4
Consumers Energy Company [Member] | Interest Expense [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund				12
Consumers Energy Company [Member] | Interest Income [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund				6
Consumers Energy Company [Member] | General Taxes [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund				5
Consumers Energy Company [Member] | Refund Of Taxes Paid Receivable [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund		42
Consumers Energy Company [Member] | Refund Of Interest Paid Receivable [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund		12
Consumers Energy Company [Member] | Interest Receivable [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund		$ 6
Consumers Energy Company [Member] | Plant, Property, And Equipment [Member] | Settlement with Taxing Authority [Member]
Guarantees And Other Contingencies [Line Items]
Tax examination refund				19
Guarantees [Member]
Guarantees And Other Contingencies [Line Items]
Expiration Date	[1]		Indefinite
Maximum obligation	[1]		$ 48
Indemnity Obligations From Stock And Asset Sales Agreements [Member]
Guarantees And Other Contingencies [Line Items]
Expiration Date	[2]		Indefinite
Maximum obligation	[2]		$ 153
Carrying Amount	[2]		7
Tax And Other Indemnity Obligations [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Carrying Amount			1
MCV PPA [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			3,010
Purchase Obligations Due in Year One			326
Purchase Obligations Due in Year Two			331
Purchase Obligations Due in Year Three			330
Purchase Obligations Due in Year Four			344
Purchase Obligations Due in Year Five			325
Purchase Obligations Due After Year Five			$ 1,354
Term of Unrecorded Unconditional Purchase Obligations			35 years
Unrecorded Unconditional Purchase Obligations, Minimum Quantity Required | MW			1,240
Unrecorded Unconditional Purchase Obligation Capacity Charge Per Mwh | $ / MWh			10.14
Unrecorded Unconditional Purchase Obligation, Annual Contribution to Renewable Resources Program By Counterparty			$ 5
Unrecorded Unconditional Purchase Obligation, Contract Extension Period			5 years
Unrecorded Unconditional Purchase Obligation, Purchases			$ 305	282	$ 300
Palisades PPA [Member]
Guarantees And Other Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligations, Maximum Quantity | MW			798
Palisades PPA [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			$ 1,994
Purchase Obligations Due in Year One			354
Purchase Obligations Due in Year Two			365
Purchase Obligations Due in Year Three			376
Purchase Obligations Due in Year Four			388
Purchase Obligations Due in Year Five			398
Purchase Obligations Due After Year Five			113
Unrecorded Unconditional Purchase Obligation, Purchases			$ 363	352	302
Unrecorded Unconditional Purchase Obligations, Maximum Quantity | MW			798
Related Parties PPA [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			$ 899
Purchase Obligations Due in Year One			81
Purchase Obligations Due in Year Two			82
Purchase Obligations Due in Year Three			86
Purchase Obligations Due in Year Four			88
Purchase Obligations Due in Year Five			88
Purchase Obligations Due After Year Five			474
Other PPA [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			3,453
Purchase Obligations Due in Year One			247
Purchase Obligations Due in Year Two			253
Purchase Obligations Due in Year Three			229
Purchase Obligations Due in Year Four			231
Purchase Obligations Due in Year Five			233
Purchase Obligations Due After Year Five			2,260
Unrecorded Unconditional Purchase Obligation, Purchases			348	$ 347	$ 354
PPA [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			9,356
Purchase Obligations Due in Year One			1,008
Purchase Obligations Due in Year Two			1,031
Purchase Obligations Due in Year Three			1,021
Purchase Obligations Due in Year Four			1,051
Purchase Obligations Due in Year Five			1,044
Purchase Obligations Due After Year Five			4,201
Other Purchase Obligations [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			1,922
Purchase Obligations Due in Year One			931
Purchase Obligations Due in Year Two			376
Purchase Obligations Due in Year Three			187
Purchase Obligations Due in Year Four			132
Purchase Obligations Due in Year Five			32
Purchase Obligations Due After Year Five			264
Other Purchase Obligations [Member] | Consumers Energy Company [Member]
Guarantees And Other Contingencies [Line Items]
Purchase Obligations Total			1,651
Purchase Obligations Due in Year One			895
Purchase Obligations Due in Year Two			347
Purchase Obligations Due in Year Three			157
Purchase Obligations Due in Year Four			102
Purchase Obligations Due in Year Five			19
Purchase Obligations Due After Year Five			$ 131

[1] At Consumers, this obligation comprises a guarantee provided to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department's failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers. At CMS Energy, the guarantee obligations comprise Consumers' guarantee to the U.S. Department of Energy and CMS Energy's 1994 guarantee of non-recourse revenue bonds issued by Genesee. For additional details on this guarantee, see Note 20, Variable Interest Entities.

[2] These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities.