|
Fair Value Measurements (Assets And Liabilties Measured At Fair Value On A Recurring Basis) (Details) (USD $)
In Millions, unless otherwise specified |
Sep. 30, 2012
|
Dec. 31, 2011
|
|---|---|---|
| Cash equivalents | $ 60 | $ 109 |
| Restricted cash equivalents | 14 | 15 |
| Nonqualified deferred compensation plan assets | 5 | 4 |
| Commodity contracts | 6 | 3 |
| Total | 214 | 245 |
| Nonqualified deferred compensation plan liabilities | 5 | 4 |
| Commodity contracts | 6 | 7 |
| Total | 11 | 11 |
|
Consumers Energy Company [Member]
|
||
| Cash equivalents | 17 | 56 |
| Restricted cash equivalents | 13 | 14 |
| Nonqualified deferred compensation plan assets | 3 | 3 |
| Commodity contracts | 4 | 2 |
| Total | 155 | 185 |
| Nonqualified deferred compensation plan liabilities | 3 | 3 |
| Total | 3 | 3 |
|
Fair Value, Inputs, Level 1 [Member]
|
||
| Cash equivalents | 60 | 109 |
| Restricted cash equivalents | 14 | 15 |
| Nonqualified deferred compensation plan assets | 5 | 4 |
| Commodity contracts | 1 | 1 |
| Total | 209 | 243 |
| Nonqualified deferred compensation plan liabilities | 5 | 4 |
| Total | 5 | 4 |
|
Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member]
|
||
| Cash equivalents | 17 | 56 |
| Restricted cash equivalents | 13 | 14 |
| Nonqualified deferred compensation plan assets | 3 | 3 |
| Total | 151 | 183 |
| Nonqualified deferred compensation plan liabilities | 3 | 3 |
| Total | 3 | 3 |
|
Fair Value, Inputs, Level 2 [Member]
|
||
| Commodity contracts | 1 | |
| Total | 1 | |
| Commodity contracts | 3 | 3 |
| Total | 3 | 3 |
|
Fair Value, Inputs, Level 3 [Member]
|
||
| Commodity contracts | 4 | 2 |
| Total | 4 | 2 |
| Commodity contracts | 3 | 4 |
| Total | 3 | 4 |
|
Fair Value, Inputs, Level 3 [Member] | Consumers Energy Company [Member]
|
||
| Commodity contracts | 4 | 2 |
| Total | 4 | 2 |
|
Supplemental Executive Retirement Plan [Member] | Cash Equivalents [Member]
|
||
| Available for sale - Fair Value | 1 | 1 |
|
Supplemental Executive Retirement Plan [Member] | Cash Equivalents [Member] | Consumers Energy Company [Member]
|
||
| Available for sale - Fair Value | 1 | 1 |
|
Supplemental Executive Retirement Plan [Member] | Mutual Fund [Member]
|
||
| Available for sale - Fair Value | 128 | 113 |
|
Supplemental Executive Retirement Plan [Member] | Mutual Fund [Member] | Consumers Energy Company [Member]
|
||
| Available for sale - Fair Value | 86 | 74 |
|
Supplemental Executive Retirement Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]
|
||
| Available for sale - Fair Value | 1 | 1 |
|
Supplemental Executive Retirement Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member] | Consumers Energy Company [Member]
|
||
| Available for sale - Fair Value | 1 | 1 |
|
Supplemental Executive Retirement Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member]
|
||
| Available for sale - Fair Value | 128 | 113 |
|
Supplemental Executive Retirement Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member] | Consumers Energy Company [Member]
|
||
| Available for sale - Fair Value | 86 | 74 |
|
CMS Energy Common Stock [Member] | Consumers Energy Company [Member]
|
||
| Available for sale - Fair Value | 31 | 35 |
|
CMS Energy Common Stock [Member] | Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member]
|
||
| Available for sale - Fair Value | $ 31 | $ 35 |