Financings And Capitalization (Narrative) (Details) (USD $)	12 Months Ended		24 Months Ended
	Dec. 31, 2014		Dec. 31, 2014		Dec. 31, 2013
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends	$ 3,700,000,000		$ 3,700,000,000
Common stock dividends from Consumers	457,000,000
Common stock, shares authorized	350,000,000		350,000,000		350,000,000
Par value of Common Stock	$ 0.01		$ 0.01
Shares of Preferred Stock authorized	10,000,000		10,000,000
Par value of Preferred Stock	$ 0.01		$ 0.01
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Maximum allowed short term securities outstanding under FERC Authorization	800,000,000		800,000,000
Maximum allowed long-term securites outstanding under FERC Authorization	1,900,000,000		1,900,000,000
Long-term securities, remaining availability under FERC Authorization	1,400,000,000		1,400,000,000
Unrestricted retained earnings	768,000,000		768,000,000
Common stock, shares authorized	125,000,000		125,000,000		125,000,000
Shares of Preferred Stock authorized	7,500,000		7,500,000		7,500,000
Par value of Preferred Stock	$ 100		$ 100		100
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Weighted average annual interest rate	0.49%		0.49%
Short-term debt, authorized borrowings	500,000,000
Short-term borrowings outstanding	60,000,000		60,000,000
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	250,000,000		250,000,000
Average short-term borrowings	11,000,000
Weighted average annual interest rate	0.85%		0.85%
Short-term borrowings outstanding	0		0
Continuous Equity Program [Member]
Financing And Capitalization [Line Items]
Aggregate sales price of an equity offering program			50,000,000
Revolving Credit Facilities December 20, 2018 [Member]
Financing And Capitalization [Line Items]
Amount of Facility	550,000,000	[1]	550,000,000	[1]
Revolving Credit Facilities December 20, 2018 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility	$ 650,000,000	[2]	$ 650,000,000	[2]

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

[2] Obligations under this facility are secured by FMBs of Consumers.