Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Allowances for doubtful accounts receivable	$ 37	$ 40
Allowances for doubtful notes receivable	8	8
Common stock, shares authorized	350,000,000	350,000,000
Common stock, shares outstanding	276,000,000	275,200,000
Consumers Energy Company [Member]
Allowances for doubtful accounts receivable	$ 36	$ 39
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares outstanding	84,100,000	84,100,000