Financings And Capitalization (Narrative) (Details) - USD ($)	1 Months Ended	9 Months Ended
Oct. 25, 2017	Sep. 30, 2017
Financing And Capitalization [Line Items]
Debt issuance		$ 885,000,000
Debt retirement, principal		430,000,000
Unrestricted retained earnings		4,500,000,000
Common stock dividends from Consumers		347,000,000
Term Loan [Member]
Financing And Capitalization [Line Items]
Debt issuance		$ 180,000,000
Debt instrument, extension term		1 year
CMS Energy [Member]
Financing And Capitalization [Line Items]
Debt issuance		$ 350,000,000
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Debt issuance		535,000,000
Debt retirement, principal		430,000,000
Unrestricted retained earnings		1,100,000,000
Consumers Energy Company [Member] \| Commercial Paper [Member]
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings		500,000,000
Short-term borrowings outstanding		$ 230,000,000
Consumers Energy Company [Member] \| FMB's 3.21% Due 2017 [Member] \| Subsequent Event [Member]
Financing And Capitalization [Line Items]
Debt retirement, principal	$ 100,000,000
Interest rate	3.21%

Debt instrument, extension term

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Financing And Capitalization [Line Items]

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No definition available.

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- Definition

Maximum borrowing capacity under the commercial paper program without consideration of any current restrictions on the amount that could be issued or the amounts currently outstanding under the program.

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No definition available.

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- Definition

This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(b))
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- Definition

Face (par) amount of debt instrument at time of issuance.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount of dividends that can be declared or paid without approval of regulatory agency.

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-Name Accounting Standards Codification
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