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Financings And Capitalization (Revolving Credit Facilities) (Details) | 3 Months Ended
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Mar. 31, 2017 USD ($)
Revolving Credit Facilities May 27, 2021 [Member] | CMS Energy [Member] |  |
Line of Credit Facility [Line Items] |  |
Expiration Date | May 27, 2021 | [1]
Amount of Facility | $ 550,000,000 | [1]
Letters of Credit Outstanding | 1,000,000 | [1]
Amount Available | 549,000,000 | [1]
Average borrowings | $ 85,000,000 |
Weighted average interest rate | 2.02% |
Revolving Credit Facilities May 27, 2021 [Member] | Consumers Energy Company [Member] |  |
Line of Credit Facility [Line Items] |  |
Expiration Date | May 27, 2021 |
Amount of Facility | $ 650,000,000 |
Letters of Credit Outstanding | 7,000,000 |
Amount Available | $ 643,000,000 |
Revolving Credit Facilities November 23, 2018 [Member] | Consumers Energy Company [Member] |  |
Line of Credit Facility [Line Items] |  |
Expiration Date | Nov. 23, 2018 | [2]
Amount of Facility | $ 250,000,000 | [2]
Amount Available | $ 250,000,000 | [2]
Revolving Credit Facilities May 9, 2018 [Member] | Consumers Energy Company [Member] |  |
Line of Credit Facility [Line Items] |  |
Expiration Date | May 09, 2018 | [2]
Amount of Facility | $ 30,000,000 | [2]
Letters of Credit Outstanding | $ 30,000,000 | [2]
[1] | During the three months ended March 31, 2017, CMS Energy's average borrowings totaled $85 million with a weighted-average interest rate of 2.02 percent. Obligations under this facility are secured by Consumers common stock.
[2] | Obligations under this facility are secured by first mortgage bonds of Consumers.

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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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- Definition Average amount borrowed under the credit facility during the period. + References No definition available. + Details
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- Definition Date the credit facility terminates, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The effective interest rate during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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