Document & Entity Information [Abstract] Document & Entity Information [Abstract] Statement [Table] Legal Entity [Axis] Entity [Domain] CMS Energy Corporation Consumer Energy Company [Member] Consumer Energy Company Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Period Focus Document Fiscal Year Focus Trading Symbol Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Income Statement [Abstract] Operating Revenue Operating Revenue Operating Expenses Fuel for electric generation Fuel For Electric Generation2 Fuel for electric generation Purchased and interchange power Cost of electricity purchased from related parties and sold during the reporting period. Purchased Power Related Parties Purchased power - related parties Cost of natural gas purchased and sold and associated transportation and storage costs during the reporting period. Cost of gas sold Maintenance and other operating expenses Other Cost and Expense, Operating, Total Other Depreciation and amortization Depreciation and amortization General taxes General taxes Insurance Recoveries Insurance settlement Insurance settlement Gain on asset sales, net Gain on asset sales, net Gain on asset sales, net Gain on asset sales, net Gain on asset sales, net Total Operating Expenses Total operating expenses Operating Income Operating Income Other Income (Expense) Interest and dividends Investment Income, Interest and Dividend, Total Allowance for equity funds used during construction Allowance for equity funds used during construction Income (loss) from equity method investees Income (Loss) from Equity Method Investees Income (Loss) from Equity Method Investments, Total Other income Other expense Other expense Other expense Other expense Total Other Income (Deductions) Total other income (expense) Interest Charges Interest on long-term debt Interest Expense, Debt, Total Other interest Allowance for borrowed funds used during construction Allowance for borrowed funds used during construction Allowance for borrowed funds used during construction Allowance for borrowed funds used during construction Interest Expense Total interest charges Income Before Income Taxes Income Before Income Taxes Income Tax Expense Benefit Income Tax Expense Income Tax Expense Income from Continuing Operations Income from Continuing Operations Income (Loss) From Discontinued Operations, Net of Tax (Tax Benefit) of $19, $(1), $19 and $(1) Income (Loss) From Discontinued Operations, Net of Tax Expense of $6, $17, $5 and $16 Loss From Discontinued Operations, Net of Tax Benefit of $(), $, $ and $() Net Income Net Income Income attributable to noncontrolling interests Income Attributable to Noncontrolling Interests Income Attributable to Noncontrolling Interests Net Income Attributable to CMS Energy Net Income Attributable to CMS Energy Preferred Stock Dividends Preferred Stock Dividends Net Income Available to Common Stockholders Net Income Available to Common Stockholders Net Income Available to Common Stockholders Amounts Attributable to Common Stockholders [Abstract] Amounts Attributable to Common Stockholders Abstract Net Income Attributable to Common Stockholders Income Loss from Continuing Operations Amounts Attributable to Continuing Operations Income (Loss) from Continuing Operations Attributable to Parent, Total Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Amounts Attributable to Discontinued Operations Amounts Attributable to Discontinued Operations Minority Interest In Net Income Loss of Consolidated Entities Abstract Income Attributable to Noncontrolling Interests Amounts Attributable to Continuing Operations Loss from Discontinued Operations Amounts Attributable to Discontinued Operations Amounts Attributable to Discontinued Operations Income Loss Before Extraordinary Items And Cumulative Effect Of Change In Accounting Principle Per Basic Share Abstract Basic Earnings Per Average Common Share Basic Earnings from Continuing Operations Income (Loss) from Continuing Operations, Per Outstanding Share, Total Income (Loss) from Discontinued Operations Basic Earnings (Loss) from Discontinued Operations Basic Loss from Discontinued Operations Earnings Per Share, Basic Basic Earnings Attributable to Common Stock Income Loss Before Extraordinary Items And Cumulative Effect Of Change In Accounting Principle Per Diluted Share Abstract Diluted Earnings Per Average Common Share Diluted Earnings from Continuing Operations Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Diluted Earnings (Loss) from Discontinued Operations Diluted Loss from Discontinued Operations Earnings Per Share, Diluted Diluted Earnings Attributable to Common Stock Common Stock, Dividends, Per Share, Declared Dividends Declared Per Common Share Dividends Declared Per Common Share Statement, Business Segments [Axis] Segment, Business [Domain] Business Intersegment, Eliminations [Member] Statement, Scenario [Axis] Scenario, Unspecified [Domain] Consolidated Statements of Income [Parenthetical] Consolidated Statements of Income [Parenthetical] Discontinued Operation Tax Effect of Discontinued Operation Tax expense included in Income (Loss) From Discontinued Operations Discontinued Operation, Tax Effect of Discontinued Operation, Total Consolidated Statements of Cash Flow (Parenthetical) Cash and Cash Equivalents, Period Increase (Decrease) [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Cash Flows from Operating Activities Adjustments to reconcile net income to net cash provided by operating activities Depreciation and amortization Depreciation, Depletion and Amortization, Total Deferred income taxes and investment tax credit Deferred Income Taxes and Tax Credits, Total Postretirement benefits expense Pension and Other Postretirement Benefit Expense, Total Capital lease and other amortization Amortization of Financing Costs and Discounts, Total Bad debt expense Gain due to expiration of indemnification Gain on expiration of indemnification Amount represents the difference between the fair value of the payments made and the carrying amount of the long-term debt with related parties at the time of its extinguishment. Gain On Extinguishment Of Long Term Debt Related Parties Gain on extinguishment of long-term debt, related parties Gain on extinguishment of long-term debt Adjustments Noncash Items To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities Other non-cash operating activities Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities, Total Postretirement benefits contributions Postretirement benefits contributions Pension and Other Postretirement Benefit Contributions, Total Changes in other assets and liabilities: Increase in accounts receivable and accrued revenues Decrease (increase) in accounts receivable, notes receivable, and accrued revenue The net change during the reporting period in underrecoveries of power supply and gas costs that represent receivables that will be recovered from customers. Decrease In Accrued Power Supply And Gas Revenue Decrease (increase) in accrued power supply revenue Decrease (increase) in inventories Increase (Decrease) in Inventories, Total Increase (decrease) in accounts payable trade Increase (decrease) in accounts payable Increase (decrease) in taxes and accrued expenses Increase (decrease) in accrued expenses Increase (Decrease) in Accrued Liabilities, Total Decrease (increase) in other current and non-current assets Decrease (increase) in other current and non-current assets Decrease in other current and non-current liabilities Increase (decrease) in other current and non-current liabilities Decrease in other current and non-current liabilities Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash Flows from Investing Activities Capital expenditures (excludes assets placed under capital lease) Capital expenditures (excludes assets placed under capital lease) Payments to Acquire Productive Assets, Total Cost to retire property Cost to retire property Proceeds from sale of assets Proceeds from Sale of Productive Assets, Total Cash divested from deconsolidation Cash effect of deconsolidation of partnerships Decrease in restricted cash and cash equivalents Restricted cash and cash equivalents Increase (Decrease) in Restricted Cash, Total Other investing Other investing activities Other investing activities Other investing activities Other investing activities Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash Flows from Financing Activities Proceeds from issuance of notes, bonds, and other long-term debt Proceeds from issuance of long-term debt Proceeds from Issuance of Long-term Debt, Total Proceeds from EnerBank notes, net Proceeds from (Repayments of) Notes Payable, Total Issuance of common stock Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options, Total Retirement of bonds and other long-term debt, including related parties Retirement of long-term debt Repayments of Long-term Debt, Total Payment of common stock dividends Payment of common stock dividends Payment of preferred stock dividends Payment of preferred stock dividends Stockholder's contribution Payment of capital lease and finance lease obligations Payment of capital and finance lease obligations Debt issuance costs, financing fees, and other Other financing costs Debt issuance costs, financing fees, and other Debt issuance costs, financing fees, and other Net Cash Provided by (Used in) Financing Activities Net cash (used in) provided by financing activities The net change between the beginning and ending balance of cash and cash equivalents, including changes in cash and cash equivalents included in assets held for sale. Net Increase in Cash and Cash Equivalents Net Increase in Cash and Cash Equivalents, Including Assets Held for Sale Changes in cash and cash equivalents included in assets held for sale Changes in Cash and Cash Equivalents included in Assets Held for Sale Decrease (Increase) in Cash and Cash Equivalents Included in Assets Held for Sale Net Decrease in Cash and Cash Equivalents Net Increase in Cash and Cash Equivalents Net Increase in Cash and Cash Equivalents Cash and cash equivalents Cash and Cash Equivalents, End of Period Cash and Cash Equivalents, Beginning of Period Cash and Cash Equivalents, at Carrying Value, Total Statement of Financial Position [Abstract] Assets Abstract Assets Restricted cash and cash equivalents Accounts Receivable Net Current Accounts receivable and accrued revenue, less allowances Accounts Receivable, Net, Current, Total Notes receivable Underrecoveries of power supply and gas costs that represent amounts that will be recovered from customers within one year of the balance sheet date. Accrued Power Supply Accrued power supply revenue Accounts receivable - related parties Due from Related Parties, Current, Total Inventories at average cost Gas in underground storage Materials and supplies Generating plant fuel stock Deferred property taxes Deferred Costs, Current, Total Regulatory assets Assets held for sale current Assets held for sale Assets held for sale Prepayments and other Prepayments and other current assets Prepayments and other current assets Assets, Current Total current assets Plant, Property & Equipment (at cost) Carrying amount at the balance sheet date for long-lived assets used in the normal conduct of business and not intended for resale. This can include land, physical structures, machinery, vehicles, furniture, computer equipment, similar items, including certain intangible assets. Amount is not net of depreciation, depletion, and amortization, and does not include construction work in progress. Plant And Property Gross Plant, property & equipment, gross Accumulated Depreciation, Depletion and Amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Less accumulated depreciation, depletion, and amortization Less accumulated depreciation, depletion and amortization Carrying amount at the balance sheet date for long-lived assets, including certain intangible assets, used in the normal conduct of business and not intended for resale, net of accumulated depreciation, depletion and amortization. Amount does not include construction work in progress. Plant And Property Net Plant, property & equipment, net Plant, property & equipment, net Construction work in progress Construction work in progress Construction work in progress Public Utilities, Property, Plant and Equipment, Net Total plant, property & equipment Regulated Entity Other Assets Noncurrent (Abtract) Non-current Assets Regulatory assets noncurrent Regulatory assets Notes and Loans Receivable Net Noncurrent Notes receivable, less allowances of $5 in 2010 and $6 in 2009 Notes receivable, less allowances Investments In Affiliates Subsidiaries Associates and Joint Ventures Investments Investments Assets held for sale Other Assets Noncurrent Other non-current assets Other non-current assets Assets, Noncurrent Total non-current assets Assets Total Assets Liabilities and Stockholders Equity Abstract Liabilities and Equity Current portion of long-term debt, capital and finance lease obligations Debt, Current, Total Notes payable Accounts payable Accounts Payable, Current, Total Current regulatory liabilities that represent obligations to make refunds to customers for various reasons including overpayment. Accrued rate refunds Accounts payable - related parties Due to Related Parties, Current, Total Accrued interest Interest and Dividends Payable, Current, Total Accrued taxes Taxes Payable, Current, Total Deferred income taxes Regulatory liabilities Regulatory Liability, Current, Total Liabilities held for sale Liabilities of Disposal Group, Including Discontinued Operation, Current, Total Other liabilities current Other current liabilities Other current liabilities Liabilities, Current Total current liabilities Non-current Liabilities Long-term debt Long-term debt Non-current portion of capital and finance lease obligations Non-current portion of capital and finance lease obligations Regulatory Liability, Noncurrent Regulatory liabilities Regulatory Liability, Noncurrent, Total Postretirement benefits Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent, Total Asset retirement obligations Asset Retirement Obligations, Noncurrent, Ending Balance Asset retirement obligation Deferred investment tax credit Deferred tax liabilities noncurrent Deferred income taxes Other liabilities noncurrent Other non-current liabilities Other non-current liabilities Liabilities, Noncurrent Total non-current liabilities Commitments and Contingencies 2009 Commitments and Contingencies (notes 3,4,5,7, and 8) Capitalization Common stockholders equity Equity Common stock value Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common stock Common Stock, Value, Issued, Total Additional Paid in Capital Common Stock Additional Paid in Capital, Common Stock, Ending Balance Additional Paid in Capital, Common Stock, Beginning Balance Other paid-in capital Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated other comprehensive income (loss) Accumulated other comprehensive loss Retained Earnings Accumulated Deficit Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Retained earnings (Accumulated deficit) Retained earnings (accumulated deficit) Total common stockholders' equity Stockholders' Equity Attributable to Parent, Ending Balance Stockholders' Equity Attributable to Parent, Beginning Balance Total common stockholders equity Preferred stock Value Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred stock Preferred stock Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Noncontrolling interests Noncontrolling interests Total equity Total Equity, end Total Equity, beginning Total equity Liabilities and Stockholders' Equity Total Liabilities and Equity Consolidated Balance Sheets [Parenthetical] Consolidated Balance Sheets [Parenthetical] Allowances for doubtful accounts receivable Allowance for Doubtful Accounts Receivable, Current, Ending Balance Allowance for Doubtful Accounts Receivable, Current, Beginning Balance Allowances for doubtful notes receivable Allowances for doubful notes receivable of $5 in 2009 and $34 in 2008 Common stock, shares authorized Common stock, shares outstanding Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Statement of Stockholders' Equity [Abstract] Common stock issued, value Common stock repurchased, value Conversion option on convertible debt, value Conversion option on convertible debt Other Comprehensive Income Minimum Pension Liability Net Adjustment Net of Tax Retirement benefits liability adjustments Retirement benefits liability adjustments Retirement benefits liability adjustments (a) Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Unrealized gain (loss) on investments, net of tax of $0, $0, $0, and $0, respectively Preferred stock dividends declared