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Regulatory Matters (Schedule of Components of the Rate Increase Authorized by the MPSC and the Rate Increase Originally Requested by Consumers) (Details) (Gas Rate Case [Member], Consumers Energy Company [Member], USD $) In Millions | 1 Months Ended |
--- | --- | ---
May 31, 2011 | Aug. 31, 2010
Annual Rate Increase Authorized by MPSC | $ 31 |
Annual Rate Increase Requested by Consumers |  | 55
Difference Between Rate Increase Authorized And Requested | (24) |
Investment in Rate Base [Member] |  |
Annual Rate Increase Authorized by MPSC | 29 |
Annual Rate Increase Requested by Consumers |  | 30
Difference Between Rate Increase Authorized And Requested | (1) |
Impact Of Sales Declines [Member] |  |
Annual Rate Increase Authorized by MPSC | 15 |
Annual Rate Increase Requested by Consumers |  | 4
Difference Between Rate Increase Authorized And Requested | 11 |
Recovery Of Operating And Maintenance Costs [Member] |  |
Annual Rate Increase Authorized by MPSC | 2 |
Annual Rate Increase Requested by Consumers |  | 16
Difference Between Rate Increase Authorized And Requested | (14) |
Cost Of Capital [Member] |  |
Annual Rate Increase Authorized by MPSC | (15) |
Annual Rate Increase Requested by Consumers |  | 5
Difference Between Rate Increase Authorized And Requested | $ (20) |

X
- Definition The annual rate increase authorized by the Public Service Commission. + Details
Name: | cms_AnnualRateIncreaseAuthorized
Namespace Prefix: | cms
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The annual rate increase requested by Consumers. + Details
Name: | cms_AnnualRateIncreaseRequested
Namespace Prefix: | cms
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The difference between the amount of the rate increase requested and the amount of the rate increase authorized by the Public Service Commission. + Details
Name: | cms_DifferenceBetweenRateIncreaseAuthorizedAndRequested
Namespace Prefix: | cms
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration