Notes Receivable (Policy)	3 Months Ended
Notes Receivable (Policy)	Mar. 31, 2012
Notes Receivable [Abstract]
Allowance for Loan Losses Policy	EnerBank provides unsecured consumer installment loans for financing home improvements. These loans totaled $477 million, net of an allowance for loan losses of $5 million, at March 31, 2012, and $480 million, net of an allowance for loan losses of $5 million, at December 31, 2011. At March 31, 2012, $24 million of EnerBank's loans were classified as current notes receivable and $453 million were classified as non-current notes receivable on CMS Energy's consolidated balance sheets. At December 31, 2011, $19 million of EnerBank's loans were classified as current notes receivable and $461 million were classified as non-current notes receivable on CMS Energy's consolidated balance sheets. The allowance for loan losses is a valuation allowance to reflect estimated credit losses. The allowance is increased by the provision for loan losses and decreased by loan charge-offs net of recoveries. Management estimates the allowance balance required by taking into consideration historical loan loss experience, the nature and volume of the portfolio, economic conditions, and other factors. Loan losses are charged against the allowance when the loss is confirmed, but no later than the point at which a loan becomes 120 days past due.

Disclosure of accounting policy for estimating the allowance for losses on loans and lease receivables. The disclosure may include (a) how the entity determines each element of the allowance, (b) which loans are evaluated individually and which loans are evaluated as a group, (c) how the entity determines both the allocated and unallocated portions of the allowance, (d) how the entity determines the loss factors applied to graded loans in order to develop a general allowance, and (e) what self-correcting mechanism the entity uses to reduce differences between estimated and actual losses.

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