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New Accounting Standards (Schedule Of Restricted Cash Balances) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period | $ 288 | $ 249 | $ 204
Cash from investing | (1,915) | (2,064) | (1,898)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period | 257 | 288 | 249
CMS Energy [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period |  |  |
Cash from investing | (275) | (150) | (317)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period |  |  |
Consumers Energy Company [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period | 71 | 112 | 49
Cash from investing | (1,768) | (1,801) | (1,643)
Cash and Cash Equivalents, Including Restricted Amounts, End of Period | 152 | 71 | 112
New Accounting Pronouncement, Early Adoption, Effect [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period | 22 | 42 | 32
Cash from investing |  | (20) | 10
Cash and Cash Equivalents, Including Restricted Amounts, End of Period |  | 22 | 42
New Accounting Pronouncement, Early Adoption, Effect [Member] | Consumers Energy Company [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period | $ 21 | 41 | 31
Cash from investing |  | (20) | 10
Cash and Cash Equivalents, Including Restricted Amounts, End of Period |  | $ 21 | $ 41

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- Definition Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Amount of cash inflow (outflow) of investing activities, excluding discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3574-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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