Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Allowances for doubtful accounts receivable	$ 35	$ 35
Allowances for doubtful notes receivable	5	5
Common stock, shares authorized	350.0	350.0
Common stock, shares outstanding	263.7	254.1
Consumers Energy Company [Member]
Allowances for doubtful accounts receivable	$ 33	$ 33
Common stock, shares authorized	125.0	125.0
Common stock, shares outstanding	84.1	84.1