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Stock-Based Compensation (Narrative) (Details) - shares | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Deferred Compensation Arrangements Plan Term | 10 years |
Number of shares authorized | 6,500,000 |
Maximum shares issuable per employee | 500,000 |
Shares available for grant | 4,983,931 |
Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Deferred Compensation Arrangements Plan Term | 10 years |
Number of shares authorized | 6,500,000 |
Maximum shares issuable per employee | 500,000 |
Shares available for grant | 4,983,931 |
Minimum [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percent of Initial Grant Issued on Vesting Date | 0.00% |
Minimum [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percent of Initial Grant Issued on Vesting Date | 0.00% |
Maximum [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percent of Initial Grant Issued on Vesting Date | 200.00% |
Maximum [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percent of Initial Grant Issued on Vesting Date | 200.00% |
Performance-Based Restricted Stock [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 38 months |
Vesting period | 3 years |
Performance-Based Restricted Stock [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 38 months |
Vesting period | 3 years |
Performance-Based Restricted Stock [Member] | Minimum [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 36 months |
Performance-Based Restricted Stock [Member] | Minimum [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 36 months |
Market-Based Restricted Stock [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 3 years |
Vesting period | 3 years |
Market-Based Restricted Stock [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 3 years |
Vesting period | 3 years |
Time-Lapsed Restricted Stock [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 3 years |
Time-Lapsed Restricted Stock [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 3 years |
Restricted Stock Units (RSUs) [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 1 year |
Shares forfeited | 0 | 0
Restricted Stock Units (RSUs) [Member] | Consumers Energy Company [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Service period | 1 year |
Shares forfeited | 0 | 0

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- Definition Percentage of initial grant of equity-based compensation awards earned depending on the outcome of the market condition or performance condition. + References No definition available. + Details
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- Definition The highest quantity of shares an employee can be awarded under the plan per period. + References No definition available. + Details
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- Definition Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + 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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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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