Financings And Capitalization (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended	6 Months Ended
		Sep. 30, 2014	Jun. 30, 2015
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends			$ 3,800
Common stock dividends from Consumers			254
Aggregate sales price of an equity offering program			100
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Unrestricted retained earnings			811
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings		$ 500
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
Short-term borrowings outstanding			0
Revolving Credit Facilities May 27, 2020 [Member] | CMS Energy [Member]
Financing And Capitalization [Line Items]
Amount of Facility	[1]		550
Revolving Credit Facilities May 27, 2020 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility		$ 650	$ 650	[2]

[1] During the six months ended June 30, 2015, CMS Energy's average borrowings totaled $61 million with a weighted-average interest rate of 1.43 percent. Obligations under this facility are secured by Consumers common stock.

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