Financial Instruments (Schedule Of Carrying Amounts And Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets
Securities held to maturity	$ 25	$ 21
Liabilities
EnerBank notes receivable, net of allowance for loan losses	234	233
Long-term debt, current	1,100	1,000
Other current liabilities	3	1
Carrying Amount
Assets
Long-term receivables	21	22
Notes receivable	2,464	1,857
Securities held to maturity	24	22
Liabilities
Long-term debt	13,094	11,589
Long-term payables	31	27
Fair Value
Assets
Long-term receivables	21	22
Notes receivable	2,619	1,967
Securities held to maturity	25	21
Liabilities
Long-term debt	14,371	11,630
Long-term payables	32	27
Consumers Energy Company
Liabilities
Long-term debt, current	102	26
Current portion notes receivable related party	7	7
Consumers Energy Company \| Carrying Amount
Assets
Long-term receivables	21	22
Notes receivable related party	104	106
Liabilities
Long-term debt	7,189	6,805
Consumers Energy Company \| Fair Value
Assets
Long-term receivables	21	22
Notes receivable related party	104	106
Liabilities
Long-term debt	8,035	6,833
EnerBank
Liabilities
EnerBank notes receivable, net of allowance for loan losses	234	233
Other Receivables \| Consumers Energy Company
Liabilities
Accounts receivable, current	14	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	1,245	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	25	21
Liabilities
Long-term debt	11,163	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	6,072	5,066
Fair Value, Inputs, Level 3 \| Fair Value
Assets
Long-term receivables	21	22
Notes receivable	2,619	1,967
Securities held to maturity	0	0
Liabilities
Long-term debt	1,963	1,767
Long-term payables	32	27
Fair Value, Inputs, Level 3 \| Consumers Energy Company \| Fair Value
Assets
Long-term receivables	21	22
Notes receivable related party	104	106
Liabilities
Long-term debt	$ 1,963	$ 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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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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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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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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Amount, after allowance for credit loss, of financing receivable, classified as current. Includes, but is not limited to, notes and loan receivable.

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Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

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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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