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Financial Instruments (Schedule Of Carrying Amounts And Fair Values Of Financial Instruments) (Details) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Notes and accrued interest receivable |  | $ 201 | $ 198
Other liabilities current |  | 134 | 195
Current portion of long-term debt |  | 1,300 | 1,100
DIG Note Payable [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Other liabilities current |  | 2 | 3
Carrying Amount [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] | 20 | 21
Notes receivable, Fair Value | [2] | 1,370 | 1,371
Securities held to maturity - Fair Value |  | 17 | 16
Long-term debt, Fair Value | [3] | 10,261 | 10,204
Long-term payables, Fair Value | [4] | 25 | 27
Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] | 20 | 21
Notes receivable, Fair Value | [2] | 1,453 | 1,464
Securities held to maturity - Fair Value |  | 17 | 16
Long-term debt, Fair Value | [3] | 10,273 | 10,715
Long-term payables, Fair Value | [4] | 26 | 26
Consumers Energy Company [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Notes and accrued interest receivable |  | 17 | 17
Other liabilities current |  | 103 | 159
Current portion of long-term debt |  | 693 | 343
Consumers Energy Company [Member] | Carrying Amount [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] | 20 | 21
Notes receivable, Fair Value | [5] | 17 | 17
Long-term debt, Fair Value | [6] | 5,904 | 5,904
Consumers Energy Company [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] | 20 | 21
Notes receivable, Fair Value | [5] | 17 | 17
Long-term debt, Fair Value | [6] | 6,034 | 6,236
EnerBank [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Current notes receivable |  | 203 | 200
Other Receivables [Member] | Consumers Energy Company [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Accounts receivable, current |  | 13 | 14
Fair Value, Inputs, Level 1 [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] |  |
Notes receivable, Fair Value | [2] |  |
Securities held to maturity - Fair Value |  |  |
Long-term debt, Fair Value | [3] |  |
Long-term payables, Fair Value | [4] |  |
Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] |  |
Notes receivable, Fair Value | [5] |  |
Long-term debt, Fair Value | [6] |  |
Fair Value, Inputs, Level 2 [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Securities held to maturity - Fair Value |  | 17 | 16
Long-term debt, Fair Value | [3] | 8,971 | 9,363
Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term debt, Fair Value | [6] | 4,732 | 4,883
Fair Value, Inputs, Level 3 [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] | 20 | 21
Notes receivable, Fair Value | [2] | 1,453 | 1,464
Long-term debt, Fair Value | [3] | 1,302 | 1,352
Long-term payables, Fair Value | [4] | 26 | 26
Fair Value, Inputs, Level 3 [Member] | Consumers Energy Company [Member] | Fair Value [Member] |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Long-term receivable, fair Value | [1] | 20 | 21
Notes receivable, Fair Value | [5] | 17 | 17
Long-term debt, Fair Value | [6] | $ 1,302 | $ 1,353
[1] | Includes current accounts receivable of $13 million at March 31, 2018 and $14 million at December 31, 2017.
[2] | Includes current portion of notes receivable of $203 million at March 31, 2018 and $200 million at December 31, 2017.
[3] | Includes current portion of long-term debt of $1.3 billion at March 31, 2018 and $ 1.1 billion at December 31, 2017.
[4] | Includes current portion of long-term payables of $2 million at March 31, 2018 and $3 million at December 31, 2017.
[5] | Includes current portion of notes receivable of $17 million at March 31, 2018 and $17 million at December 31, 2017.
[6] | Includes current portion of long-term debt of $693 million at March 31, 2018 and $343 million at December 31, 2017.

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- Definition 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 includes amounts related to receivables held-for-sale. + References No definition available. + Details
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