Financings And Capitalization (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended		9 Months Ended
		Oct. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Financing And Capitalization [Line Items]
Retirement of long-term debt				$ 148	$ 488
Limitation on payment of stock dividends				3,900
Common stock dividends from Consumers				359
Aggregate sales price of an equity offering program				100
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Retirement of long-term debt				48	$ 208
Unrestricted retained earnings				$ 867
Consumers Energy Company [Member] | Subsequent Event [Member]
Financing And Capitalization [Line Items]
Retirement of long-term debt		$ 50
Interest rate		2.60%
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Weighted average annual interest rate				0.52%
Short-term debt, authorized borrowings			$ 500
Short-term borrowings outstanding				$ 68
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	[2]			$ 650

[1] During the nine months ended September 30, 2015, CMS Energy's average borrowings totaled $40 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.