Other Income and Other Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Regulatory return on capital expenditures			$ 1
Return on stranded costs			1cms_RegulatoryReturnOnStrandedCosts
Fee income	8cms_FeeIncome	7cms_FeeIncome	7cms_FeeIncome
All other	3cms_OtherOtherNonoperatingIncome	3cms_OtherOtherNonoperatingIncome	2cms_OtherOtherNonoperatingIncome
Total other income	11us-gaap_OtherNonoperatingIncome	10us-gaap_OtherNonoperatingIncome	11us-gaap_OtherNonoperatingIncome
Loss on reacquired and extinguished debt	(20)	(4)
Donations	(15)cms_Donations	(4)cms_Donations	(11)cms_Donations
Civic and political expenditures	(14)cms_CivicAndPoliticalExpenditures	(5)cms_CivicAndPoliticalExpenditures	(17)cms_CivicAndPoliticalExpenditures
All other	(6)cms_OtherOtherNonoperatingExpense	(7)cms_OtherOtherNonoperatingExpense	(5)cms_OtherOtherNonoperatingExpense
Total other expense	(55)us-gaap_OtherNonoperatingExpense	(20)us-gaap_OtherNonoperatingExpense	(33)us-gaap_OtherNonoperatingExpense
Consumers Energy Company [Member]
Regulatory return on capital expenditures			1
Gain on investment		4	5
Return on stranded costs			1
Fee income	8	7	7
All other	2	3	2
Total other income	10	14	16
Donations	(15)	(4)	(11)
Civic and political expenditures	(14)	(5)	(17)
All other	(6)	(7)	(5)
Total other expense	$ (35)	$ (16)	$ (33)

The amount of expenses incurred related to civic and political activities during the period

No definition available.

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- Definition

The amount of donations made to charitable organizations during the period

+ References

No definition available.

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- Definition

Total increase in earnings in the period representing the amount of income generated related to miscellaneous fees.

+ References

No definition available.

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- Definition

The amount of other miscellaneous expense which are not identified separately as a component in Other expense table.

+ References

No definition available.

+ Details

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- Definition

The amount of other miscellaneous income which are not identified separately as a component in Other Income table.

+ References

No definition available.

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- Definition

Total increase in earnings in the period representing the regulated allowed return on stranded costs and security costs, which is expected to be recovered through rate adjustments.

+ References

No definition available.

+ Details

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- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 2

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-Name Accounting Standards Codification

-Topic 470

-SubTopic 50

-Section 40

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12355-112629

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The aggregate amount of other expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating expense recognized during the period. Such amounts may include: (a) unusual costs, (b) loss on foreign exchange transactions, (c) losses on securities (net of profits), and (d) miscellaneous other expense items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 9

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.9)

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- Definition

The aggregate amount of other income amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) profits on securities (net of losses), and (d) miscellaneous other income items.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.7)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Article 5

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- Definition

Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 360

-Section 25

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-Topic 980

-SubTopic 340

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44278-110382

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