Contingencies And Commitments (Guarantees) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Consumers Energy Company [Member]
Guarantor Obligations [Line Items]
Guarantee Description	Indemnity obligations and other guarantees
Expiration Date	Various through August 2029
Maximum obligation	$ 30	[1]
Carrying Amount	$ 1
Guarantees [Member]
Guarantor Obligations [Line Items]
Guarantee Description	Guarantees
Expiration Date	Various through March 2021
Maximum obligation	$ 51	[1]
Indemnity Obligations From Asset Sales And Other Agreements [Member]
Guarantor Obligations [Line Items]
Guarantee Description	Indemnity obligations from asset sales   and other agreements
Expiration Date	Various through August 2029
Maximum obligation	$ 143	[2]
Carrying Amount	$ 8

[1] In the normal course of business, CMS Energy and its subsidiaries have provided guarantees and other indemnities to counterparties to facilitate commercial transactions. If a counterparty incurs losses due to nonperformance or nonpayment under the contract terms, CMS Energy or one of its subsidiaries could be required to pay the counterparty.

[2] 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 power purchase agreements, 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.