Notes Receivable (Schedule Of Delinquency Status Of EnerBank's Consumer Loans) (Details) (EnerBank USA [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
EnerBank USA [Member]
Past Due 30-59 Days	$ 1		$ 1
Past Due 60-89 Days	1
Past Due Over 90 Days	1		1
Total Delinquent	3		2
Current	510		478
Total Outstanding	513	[1]	480	[1]
Loans modified as troubled debt restructurings	$ 1		$ 1

[1] In Millions September 30, 2012December 31, 2011Carrying Fair ValueCarrying Amount Total Level 1 Level 2 Level 3 Amount Fair Value CMS Energy, including ConsumersSecurities held to maturity$ 8$ 9$ -$ 9$ -$ 7$ 7Notes receivable1 513 541 - - 541 480 504Long-term debt2 7,199 8,251 - 8,251 - 7,073 8,025ConsumersLong-term debt3$ 4,348$ 4,987$ -$ 4,987$ -$ 4,326$ 4,882Includes current portion of notes receivable of $27 million at September 30, 2012 and $19 million at December 31, 2011.