Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Allowances for doubtful accounts receivable	$ 35	$ 25
Allowances for doubtful notes receivable	5	5
Common stock, shares authorized	350.0	350.0
Common stock, shares outstanding	254.1	249.6
Consumers Energy Company [Member]
Allowances for doubtful accounts receivable	$ 33	$ 23
Common stock, shares authorized	125.0	125.0
Common stock, shares outstanding	84.1	84.1