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Quarterly Financial And Common Stock Information (Details) (USD $) In Millions, except Per Share data, unless otherwise specified | 3 Months Ended | 12 Months Ended
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Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating Revenue | $ 1,758 us-gaap_Revenues |  | $ 1,430 us-gaap_Revenues |  | $ 1,468 us-gaap_Revenues |  | $ 2,523 us-gaap_Revenues |  | $ 1,736 us-gaap_Revenues |  | $ 1,445 us-gaap_Revenues |  | $ 1,406 us-gaap_Revenues |  | $ 1,979 us-gaap_Revenues |  | $ 7,179 us-gaap_Revenues |  | $ 6,566 us-gaap_Revenues |  | $ 6,253 us-gaap_Revenues
Operating Income (Loss) | 273 us-gaap_OperatingIncomeLoss |  | 236 us-gaap_OperatingIncomeLoss |  | 235 us-gaap_OperatingIncomeLoss |  | 408 us-gaap_OperatingIncomeLoss |  | 264 us-gaap_OperatingIncomeLoss |  | 317 us-gaap_OperatingIncomeLoss |  | 232 us-gaap_OperatingIncomeLoss |  | 329 us-gaap_OperatingIncomeLoss |  | 1,152 us-gaap_OperatingIncomeLoss |  | 1,142 us-gaap_OperatingIncomeLoss |  | 1,003 us-gaap_OperatingIncomeLoss
Net Income | 97 us-gaap_ProfitLoss |  | 94 us-gaap_ProfitLoss |  | 84 us-gaap_ProfitLoss |  | 204 us-gaap_ProfitLoss |  | 102 us-gaap_ProfitLoss |  | 127 us-gaap_ProfitLoss |  | 81 us-gaap_ProfitLoss |  | 144 us-gaap_ProfitLoss |  | 479 us-gaap_ProfitLoss |  | 454 us-gaap_ProfitLoss |  | 384 us-gaap_ProfitLoss
Income Attributable to Noncontrolling Interests | 1 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest |  |  |  | 1 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest |  |  |  |  |  | 1 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest |  | 1 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest |  |  |  | 2 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest |  | 2 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest |  | 2 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
Net income attributable to CMS Energy | 96 us-gaap_NetIncomeLoss |  | 94 us-gaap_NetIncomeLoss |  | 83 us-gaap_NetIncomeLoss |  | 204 us-gaap_NetIncomeLoss |  | 102 us-gaap_NetIncomeLoss |  | 126 us-gaap_NetIncomeLoss |  | 80 us-gaap_NetIncomeLoss |  | 144 us-gaap_NetIncomeLoss |  | 477 us-gaap_NetIncomeLoss |  | 452 us-gaap_NetIncomeLoss |  | 382 us-gaap_NetIncomeLoss
Basic Earnings Per Average Common Share | $ 0.35 us-gaap_EarningsPerShareBasic | [1] | $ 0.34 us-gaap_EarningsPerShareBasic | [1] | $ 0.31 us-gaap_EarningsPerShareBasic | [1] | $ 0.77 us-gaap_EarningsPerShareBasic | [1] | $ 0.38 us-gaap_EarningsPerShareBasic | [1] | $ 0.48 us-gaap_EarningsPerShareBasic | [1] | $ 0.30 us-gaap_EarningsPerShareBasic | [1] | $ 0.55 us-gaap_EarningsPerShareBasic | [1] | $ 1.76 us-gaap_EarningsPerShareBasic |  | $ 1.71 us-gaap_EarningsPerShareBasic |  | $ 1.46 us-gaap_EarningsPerShareBasic
Diluted Earnings Per Average Common Share | $ 0.35 us-gaap_EarningsPerShareDiluted | [1] | $ 0.34 us-gaap_EarningsPerShareDiluted | [1] | $ 0.30 us-gaap_EarningsPerShareDiluted | [1] | $ 0.75 us-gaap_EarningsPerShareDiluted | [1] | $ 0.37 us-gaap_EarningsPerShareDiluted | [1] | $ 0.46 us-gaap_EarningsPerShareDiluted | [1] | $ 0.29 us-gaap_EarningsPerShareDiluted | [1] | $ 0.53 us-gaap_EarningsPerShareDiluted | [1] | $ 1.74 us-gaap_EarningsPerShareDiluted |  | $ 1.66 us-gaap_EarningsPerShareDiluted |  | $ 1.42 us-gaap_EarningsPerShareDiluted
CMS Energy [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating Income (Loss) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (6)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (6)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (8)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net Income |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 477 us-gaap_ProfitLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 452 us-gaap_ProfitLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 382 us-gaap_ProfitLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net income attributable to CMS Energy |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 477 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 452 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 382 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Consumers Energy Company [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating Revenue | 1,672 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,359 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,387 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 2,382 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,674 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,386 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,342 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,919 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 6,800 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 6,321 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 6,013 us-gaap_Revenues / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember
Operating Income (Loss) | 264 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 245 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 227 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 399 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 258 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 314 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 227 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 319 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,135 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,118 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 984 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember
Net Income | 118 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 119 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 109 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 221 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 119 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 153 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 100 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 162 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 567 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 534 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 439 us-gaap_ProfitLoss / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember
Preferred stock dividends and distribution | 1 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |  | 1 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |  |  |  | 1 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |  | 2 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 2 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 2 us-gaap_PreferredStockDividendsAndOtherAdjustments / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember
Net Income Available to Common Stockholders | $ 117 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 119 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 108 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 221 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 119 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 152 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 99 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 162 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 565 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 532 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 437 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember
Maximum [Member] | CMS Energy Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share price | $ 36.42 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 30.87 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 31.15 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 29.28 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 28.05 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 28.52 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 29.94 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 27.94 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 36.42 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 28.05 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] |
Minimum [Member] | CMS Energy Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share price | $ 29.78 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember |  | $ 28.18 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember |  | $ 28.87 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember |  | $ 26.12 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember |  | $ 25.90 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 25.86 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 25.95 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 24.76 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] | $ 29.78 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember |  | $ 25.90 us-gaap_SharePrice / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember | [2] |
[1] | The sum of the quarters may not equal annual EPS due to changes in the number of shares outstanding.
[2] | Based on New York Stock Exchange composite transactions.

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