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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.

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