Financings And Capitalization (Revolving Credit Facilities) (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Nov. 30, 2015	Dec. 31, 2015
Revolving Credit Facilities May 27, 2020 [Member]
Line of Credit Facility [Line Items]
Expiration Date	[1]		May 27, 2020
Amount of Facility	[1]		$ 550
Amount Borrowed	[1]
Letters of Credit Outstanding	[1]		$ 1
Amount Available	[1]		$ 549
Revolving Credit Facilities May 27, 2020 [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
Expiration Date	[2]		May 27, 2020
Amount of Facility	[2]		$ 650
Amount Borrowed	[2]
Letters of Credit Outstanding	[2]		$ 9
Amount Available	[2]		$ 641
Revolving Credit Facilities November 23, 2017 [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
Expiration Date	[2],[3]		Nov. 23, 2017
Amount of Facility		$ 250	$ 250	[2],[3]
Amount Borrowed	[2],[3]
Amount Available	[2],[3]		$ 250
Revolving Credit Facilities May 9, 2018 [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
Expiration Date	[2]		May 09, 2018
Amount of Facility	[2]		$ 30
Amount Borrowed	[2]
Letters of Credit Outstanding	[2]		$ 30
Short Term Secured Borrowing Accounts Receivable Sales Program [Member] | Consumers Energy Company [Member]
Line of Credit Facility [Line Items]
Short term borrowings, program terminated		$ 250

[1] Obligations under this facility are secured by Consumers common stock

[2] Obligations under this facility are secured by FMBs of Consumers.In November 2015, Consumers entered into a new $250 million credit facility and terminated its $250 million accounts receivable sales program.

[3] In November 2015, Consumers entered into a new $250 million credit facility and terminated its $250 million accounts receivable sales program.