Financings and Capitalization (Narrative) (Details) (USD $)		6 Months Ended			6 Months Ended	23 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 CMS Energy [Member]	Jun. 30, 2013 Consumers Energy Company [Member]	May 31, 2013 Consumers Energy Company [Member] $4.16 Series [Member]	Jun. 30, 2013 Short-Term Borrowings [Member] Consumers Energy Company [Member]	Apr. 25, 2013 Continuous Equity Program [Member]	Jun. 30, 2013 Senior Notes 5.5% Due June 2029 [Member]
Financing And Capitalization [Line Items]
Amount of Facility					$ 250,000,000
Accounts receivable sales facility, current borrowing capacity					250,000,000
Average short-term borrowings					10,000,000
Weighted average annual interest rate					0.94%
Number of trading days, adjusted trigger price contingencies were met							20 days
Number of trading days							30 days
Limitation on payment of stock dividends	3,300,000,000
Unrestricted retained earnings			603,000,000
Common stock dividends from Consumers		194,000,000
Aggregate sales price of an equity offering program						50,000,000
Preferred stock, par value				$ 4.16
Redemption price per share				$ 103.25
Redemption price				$ 7,000,000
Preferred shares outstanding				68,451