Consolidated Balance Sheets (Parenthetical) (USD $) In Millions | Sep. 30, 2011 | Dec. 31, 2010 |
|---|---|---|
| Allowances for doubtful accounts receivable | $ 25 | $ 25 |
| Allowances for doubtful notes receivable | 5 | 5 |
| Common stock, shares authorized | 350.0 | 350.0 |
| Common stock, shares outstanding | 252.0 | 249.6 |
Consumers Energy Company [Member] | ||
| Allowances for doubtful accounts receivable | $ 23 | $ 23 |
| Common stock, shares authorized | 125.0 | 125.0 |
| Common stock, shares outstanding | 84.1 | 84.1 |