Financings And Capitalization (Narrative) (Details) - USD ($)		1 Months Ended	3 Months Ended
		Apr. 30, 2016	Mar. 31, 2016
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends			$ 4,100,000,000
Common stock dividends from Consumers			155,000,000
Aggregate sales price of an equity offering program			100,000,000
Term Loan [Member] | Subsequent Event [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			902,000,000
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Short-term debt, authorized borrowings			500,000,000
Revolving Credit Facilities May 27, 2020 [Member] | CMS Energy [Member]
Financing And Capitalization [Line Items]
Amount of Facility	[1]		550,000,000
Revolving Credit Facilities May 27, 2020 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility	[2]		$ 650,000,000

[1] During the three months ended March 31, 2016, CMS Energy's average borrowings totaled $10 million with a weighted-average interest rate of 1.68 percent. Obligations under this facility are secured by Consumers common stock.

[2] Obligations under this facility are secured by first mortgage bonds of Consumers.