Contingencies And Commitments (Guarantees) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 MW		Dec. 31, 2013	Dec. 31, 2012
Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Expiration Date	Various through August 2029
Maximum obligation	$ 30
Carrying Amount	1
Guarantees [Member]
Guarantor Obligations [Line Items]
Expiration Date	Various through March 2021
Maximum obligation	54
Indemnity Obligations From Asset Sales And Other Agreements [Member]
Guarantor Obligations [Line Items]
Expiration Date	Various through August 2029
Maximum obligation	150	[1]
Carrying Amount	7
MCV PPA [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	3,425
Purchase Obligations Due in Year One	370
Purchase Obligations Due in Year Two	384
Purchase Obligations Due in Year Three	312
Purchase Obligations Due in Year Four	301
Purchase Obligations Due in Year Five	316
Purchase Obligations Due After Year Five	1,742
MCV PPA [Member] | Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	3,425
Purchase Obligations Due in Year One	370
Purchase Obligations Due in Year Two	384
Purchase Obligations Due in Year Three	312
Purchase Obligations Due in Year Four	301
Purchase Obligations Due in Year Five	316
Purchase Obligations Due After Year Five	1,742
Term of Unrecorded Unconditional Purchase Obligations	35 years
Unrecorded Unconditional Purchase Obligations, Minimum Quantity Required	1,240
Unrecorded Unconditional Purchase Obligation Capacity Charge Per 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	300		278	319
Palisades PPA [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	2,661
Purchase Obligations Due in Year One	331
Purchase Obligations Due in Year Two	342
Purchase Obligations Due in Year Three	352
Purchase Obligations Due in Year Four	364
Purchase Obligations Due in Year Five	375
Purchase Obligations Due After Year Five	897
Palisades PPA [Member] | Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	2,661
Purchase Obligations Due in Year One	331
Purchase Obligations Due in Year Two	342
Purchase Obligations Due in Year Three	352
Purchase Obligations Due in Year Four	364
Purchase Obligations Due in Year Five	375
Purchase Obligations Due After Year Five	897
Unrecorded Unconditional Purchase Obligation, Purchases	302		338	331
Unrecorded Unconditional Purchase Obligations, Maximum Quantity	798
Related Parties PPA [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	1,135
Purchase Obligations Due in Year One	83
Purchase Obligations Due in Year Two	83
Purchase Obligations Due in Year Three	85
Purchase Obligations Due in Year Four	85
Purchase Obligations Due in Year Five	88
Purchase Obligations Due After Year Five	711
Related Parties PPA [Member] | Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	1,135
Purchase Obligations Due in Year One	83
Purchase Obligations Due in Year Two	83
Purchase Obligations Due in Year Three	85
Purchase Obligations Due in Year Four	85
Purchase Obligations Due in Year Five	88
Purchase Obligations Due After Year Five	711
Other PPA [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	3,915
Purchase Obligations Due in Year One	254
Purchase Obligations Due in Year Two	244
Purchase Obligations Due in Year Three	245
Purchase Obligations Due in Year Four	247
Purchase Obligations Due in Year Five	224
Purchase Obligations Due After Year Five	2,701
Other PPA [Member] | Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	3,915
Purchase Obligations Due in Year One	254
Purchase Obligations Due in Year Two	244
Purchase Obligations Due in Year Three	245
Purchase Obligations Due in Year Four	247
Purchase Obligations Due in Year Five	224
Purchase Obligations Due After Year Five	2,701
Non-Related Parties [Member] | Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Unrecorded Unconditional Purchase Obligation, Purchases	354		345	314
Other Purchase Obligations [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	1,812
Purchase Obligations Due in Year One	755
Purchase Obligations Due in Year Two	418
Purchase Obligations Due in Year Three	330
Purchase Obligations Due in Year Four	80
Purchase Obligations Due in Year Five	76
Purchase Obligations Due After Year Five	153
Other Purchase Obligations [Member] | Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Purchase Obligations Total	1,546
Purchase Obligations Due in Year One	721
Purchase Obligations Due in Year Two	389
Purchase Obligations Due in Year Three	301
Purchase Obligations Due in Year Four	51
Purchase Obligations Due in Year Five	47
Purchase Obligations Due After Year Five	$ 37

[1] The majority of this amount arises from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy, other than Consumers, indemnified the purchaser for losses resulting from various matters, including claims related to tax disputes, claims related to PPAs, and defects in title to the assets or stock sold to the purchaser by CMS Energy subsidiaries. Except for items described elsewhere in this Note, CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities.