Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Allowances for doubtful accounts receivable	$ 40	$ 33
Allowances for doubtful notes receivable	8	5
Common stock, shares authorized	350,000,000	350,000,000
Common stock, shares outstanding	275,200,000	266,100,000
Consumers Energy Company [Member]
Allowances for doubtful accounts receivable	$ 39	$ 31
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares outstanding	84,100,000	84,100,000