Financings And Capitalization (Narrative) (Details) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015		Sep. 30, 2014
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends	$ 3,800,000,000
Common stock dividends from Consumers	122,000,000
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Unrestricted retained earnings	860,000,000
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings			500,000,000
Short-term borrowings outstanding	0
Short Term Secured Borrowing Accounts Receivable Sales Program [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of accounts receivable eligible for transfer	250,000,000
Short-term borrowings outstanding	0
Revolving Credit Facilities December 20, 2018 [Member] | CMS Energy [Member]
Financing And Capitalization [Line Items]
Amount of Facility	550,000,000	[1]
Revolving Credit Facilities December 20, 2018 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility	$ 650,000,000	[2]

[1] During the three months ended March 31, 2015, CMS Energy’s average borrowings totaled $68 million with a weighted-average interest rate of 1.42 percent. Obligations under this facility are secured by Consumers common stock.

[2] Obligations under this facility are secured by FMBs of Consumers.