Financings And Capitalization (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Financing And Capitalization [Line Items]
Limitation on payment of stock dividends		$ 3,900
Common stock dividends from Consumers		$ 474
Common stock, shares authorized		350,000,000	350,000,000
Par value of Common Stock		$ 0.01
Shares of Preferred Stock authorized		10,000,000
Par value of Preferred Stock		$ 0.01
Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Maximum allowed short term securities outstanding under FERC Authorization		$ 800
Maximum allowed long-term securites outstanding under FERC Authorization		1,900
Long-term securities, remaining availability under FERC Authorization		900
Short-term debt, authorized borrowings		800
Short-term borrowings outstanding		249
Unrestricted retained earnings		$ 884
Common stock, shares authorized		125,000,000	125,000,000
Consumers Energy Company [Member] | Commercial Paper [Member]
Financing And Capitalization [Line Items]
Weighted average annual interest rate		0.91%
Short-term debt, authorized borrowings		$ 500
Short-term borrowings outstanding		249
Continuous Equity Program [Member]
Financing And Capitalization [Line Items]
Aggregate sales price of an equity offering program		$ 100
Number of Shares Issued		888,610
Average Price Per Share		$ 33.76
Proceeds		$ 30
Revolving Credit Facilities May 27, 2020 [Member]
Financing And Capitalization [Line Items]
Amount of Facility	[1]	550
Revolving Credit Facilities May 27, 2020 [Member] | Consumers Energy Company [Member]
Financing And Capitalization [Line Items]
Amount of Facility	[2]	$ 650

[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.