Financial Instruments (Schedule Of Carrying Amounts And Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets
Securities held to maturity	$ 22	$ 21
Liabilities
Current portion of notes receivable	250	233
Other current liabilities	2	1
Long-term debt, current	821	974
Carrying Amount
Assets
Long-term receivables	21	22
Notes receivable	2,018	1,857
Securities held to maturity	22	22
Liabilities
Long-term debt	11,926	11,589
Long-term payables	27	27
Fair Value
Assets
Long-term receivables	21	22
Notes receivable	2,126	1,967
Securities held to maturity	22	21
Liabilities
Long-term debt	12,404	11,630
Long-term payables	28	27
Consumers Energy Company
Liabilities
Long-term debt, current	26	26
Current portion notes receivable related party	7	7
Consumers Energy Company \| Carrying Amount
Assets
Long-term receivables	21	22
Notes receivable related party	105	106
Liabilities
Long-term debt	6,591	6,805
Consumers Energy Company \| Fair Value
Assets
Long-term receivables	21	22
Notes receivable related party	105	106
Liabilities
Long-term debt	6,897	6,833
EnerBank
Liabilities
Current portion of notes receivable	250	233
Other Receivables \| Consumers Energy Company
Liabilities
Accounts receivable, current	13	14
Fair Value, Inputs, Level 1 \| Fair Value
Assets
Long-term receivables	0	0
Notes receivable	0	0
Securities held to maturity	0	0
Liabilities
Long-term debt	1,147	459
Long-term payables	0	0
Fair Value, Inputs, Level 1 \| Consumers Energy Company \| Fair Value
Assets
Long-term receivables	0	0
Notes receivable related party	0	0
Liabilities
Long-term debt	0	0
Fair Value, Inputs, Level 2 \| Fair Value
Assets
Long-term receivables	0	0
Notes receivable	0	0
Securities held to maturity	22	21
Liabilities
Long-term debt	9,418	9,404
Long-term payables	0	0
Fair Value, Inputs, Level 2 \| Consumers Energy Company \| Fair Value
Assets
Long-term receivables	0	0
Notes receivable related party	0	0
Liabilities
Long-term debt	5,058	5,066
Fair Value, Inputs, Level 3 \| Fair Value
Assets
Long-term receivables	21	22
Notes receivable	2,126	1,967
Securities held to maturity	0	0
Liabilities
Long-term debt	1,839	1,767
Long-term payables	28	27
Fair Value, Inputs, Level 3 \| Consumers Energy Company \| Fair Value
Assets
Long-term receivables	21	22
Notes receivable related party	105	106
Liabilities
Long-term debt	$ 1,839	$ 1,767

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Fair value portion of amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties.

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Amounts due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer) for goods or services (including trade receivables) that have been delivered or sold in the normal course of business.

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Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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An amount representing an agreement for an unconditional promise by the maker to pay the Company (holder) a definite sum of money within one year from the balance sheet date (or the normal operating cycle, whichever is longer), net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

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Amounts due from parties associated with the reporting entity as evidenced by a written promise to pay, due within 1 year (or 1 business cycle).

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