Financial Instruments (Schedule Of Carrying Amounts And Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets
Securities held to maturity	$ 31	$ 26
Liabilities
EnerBank notes receivable, net of allowance for loan losses	272	242
Long-term debt, current	1,800	1,100
Other current liabilities	6	1
Carrying Amount
Assets
Long-term receivables	18	20
Notes receivable	2,907	2,500
Securities held to maturity	30	26
Liabilities
Long-term debt	15,054	13,062
Long-term payables	31	30
Fair Value
Assets
Long-term receivables	18	20
Notes receivable	3,259	2,652
Securities held to maturity	31	26
Liabilities
Long-term debt	17,104	14,185
Long-term payables	33	32
Consumers Energy Company
Liabilities
Long-term debt, current	537	202
Current portion notes receivable related party	7	7
Consumers Energy Company \| Carrying Amount
Assets
Long-term receivables	18	20
Notes receivable related party	108	103
Liabilities
Long-term debt	7,995	7,250
Consumers Energy Company \| Fair Value
Assets
Long-term receivables	18	20
Notes receivable related party	108	103
Liabilities
Long-term debt	9,440	8,010
Other Receivables
Liabilities
Accounts receivable, current	12	13
Other Receivables \| Consumers Energy Company
Liabilities
Accounts receivable, current	12	13
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	1,185	1,197
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	31	26
Liabilities
Long-term debt	13,992	11,048
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	7,513	6,070
Fair Value, Inputs, Level 3 \| Fair Value
Assets
Long-term receivables	18	20
Notes receivable	3,259	2,652
Securities held to maturity	0	0
Liabilities
Long-term debt	1,927	1,940
Long-term payables	33	32
Fair Value, Inputs, Level 3 \| Consumers Energy Company \| Fair Value
Assets
Long-term receivables	18	20
Notes receivable related party	108	103
Liabilities
Long-term debt	1,927	1,940
EnerBank
Liabilities
EnerBank notes receivable, net of allowance for loan losses	$ 272	$ 242

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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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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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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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