Financings And Capitalization (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017 USD ($)
Financing And Capitalization [Line Items]
Unrestricted retained earnings	$ 4,400,000,000
Common stock dividends from Consumers	148,000,000
Term Loan [Member]
Financing And Capitalization [Line Items]
Debt issuance	$ 180,000,000
Debt instrument, extension term	1 year
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Unrestricted retained earnings	$ 1,100,000,000
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
Revolving Credit Facilities May 27, 2021 [Member] | CMS Energy [Member]
Financing And Capitalization [Line Items]
Amount of Facility	550,000,000	[1]
Revolving Credit Facilities May 27, 2021 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility	$ 650,000,000

[1] During the three months ended March 31, 2017, CMS Energy's average borrowings totaled $85 million with a weighted-average interest rate of 2.02 percent. Obligations under this facility are secured by Consumers common stock.