Financings And Capitalization (Narrative) (Details)	6 Months Ended
	Jun. 30, 2016 USD ($)
Financing And Capitalization [Line Items]
Unrestricted retained earnings	$ 4,200,000,000
Common stock dividends from Consumers	213,000,000
Aggregate sales price of an equity offering program	100,000,000
Term Loan [Member]
Financing And Capitalization [Line Items]
Debt issuance	$ 180,000,000
Debt instrument, extension term	1 year
CMS Energy [Member]
Financing And Capitalization [Line Items]
Debt issuance	$ 300,000,000
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Unrestricted retained earnings	974,000,000
Consumers Energy Company [Member] | Short-Term Borrowings [Member]
Financing And Capitalization [Line Items]
Maximum limitation on outstanding securities	800,000,000
Consumers Energy Company [Member] | Long-term Debt [Member]
Financing And Capitalization [Line Items]
Maximum limitation on outstanding securities	1,795,000,000
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],[2]
Revolving Credit Facilities May 27, 2021 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility	$ 650,000,000	[2],[3]

[1] During the six months ended June 30, 2016, CMS Energy's average borrowings totaled $5 million with a weighted-average interest rate of 1.68 percent. Obligations under this facility are secured by Consumers common stock.

[2] In May 2016, the expiration date of this revolving credit agreement was extended from 2020 to 2021.

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