Consolidated Statements of Changes in Equity (Parenthetical) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Retirement benefits liability adjustments, tax	$ 1	$ 0	$ 1	$ 1
Consumers Energy Company [Member]
Unrealized gain (loss) on investments, tax expense (tax benefit)		$ (1)	$ (1)	$ (1)

- Definition

The tax effect of the amount of the change in the additional minimum pension liability not yet recognized pursuant to FAS 87 as a net periodic pension cost. If the additional pension liability required to be recognized exceeds the unrecognized prior service costs, then the excess (which is the net loss not yet recognized as net periodic pension cost) is to be recorded as a separate component in other comprehensive income, before adjusting for tax effects. In a subsequent measurement, the elimination or adjustment to the amount of the minimum pension liability recorded in accumulated other comprehensive income is included in this line. Eliminated upon adoption of FAS 158.

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