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v3.3.1.900

Retirement Benefits (Schedule Of Allocation Of Plan Assets) (Details) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | $ 2,013 | $ 1,979
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 753 | 629
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1,260 | 1,350
Pension Plan [Member] | Cash and Short-Term Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 215 | 31
Pension Plan [Member] | Cash and Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 215 | 31
Pension Plan [Member] | U.S. Government and Agencies Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 19 | 30
Pension Plan [Member] | U.S. Government and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 19 | 30
Pension Plan [Member] | Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 243 | 222
Pension Plan [Member] | Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 243 | 222
Pension Plan [Member] | State and Municipal Bonds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 8 | 8
Pension Plan [Member] | State and Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 8 | 8
Pension Plan [Member] | Foreign Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 16 | 21
Pension Plan [Member] | Foreign Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 16 | 21
Pension Plan [Member] | Mutual Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 538 | 598
Pension Plan [Member] | Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 538 | 598
Pension Plan [Member] | Pooled Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 974 | 1,069
Pension Plan [Member] | Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 974 | 1,069
OPEB [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1,208 | 1,265
OPEB [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1,133 | 1,186
OPEB [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 561 | 526
OPEB [Member] | Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 526 | 494
OPEB [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 647 | 739
OPEB [Member] | Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 607 | 692
OPEB [Member] | Cash and Short-Term Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 51 | 19
OPEB [Member] | Cash and Short-Term Investments [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 48 | 18
OPEB [Member] | Cash and Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 51 | 19
OPEB [Member] | Cash and Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 48 | 18
OPEB [Member] | U.S. Government and Agencies Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 3 | 5
OPEB [Member] | U.S. Government and Agencies Securities [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 3 | 4
OPEB [Member] | U.S. Government and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 3 | 5
OPEB [Member] | U.S. Government and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 3 | 4
OPEB [Member] | Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 34 | 33
OPEB [Member] | Corporate Debt [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 32 | 31
OPEB [Member] | Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 34 | 33
OPEB [Member] | Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 32 | 31
OPEB [Member] | State and Municipal Bonds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 1
OPEB [Member] | State and Municipal Bonds [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 1
OPEB [Member] | State and Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 1
OPEB [Member] | State and Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 1
OPEB [Member] | Foreign Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 2 | 3
OPEB [Member] | Foreign Corporate Debt [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 2 | 3
OPEB [Member] | Foreign Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 2 | 3
OPEB [Member] | Foreign Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 2 | 3
OPEB [Member] | Common Stocks [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 54 | 69
OPEB [Member] | Common Stocks [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 51 | 65
OPEB [Member] | Common Stocks [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 54 | 69
OPEB [Member] | Common Stocks [Member] | Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 51 | 65
OPEB [Member] | Mutual Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 456 | 438
OPEB [Member] | Mutual Funds [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 427 | 411
OPEB [Member] | Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 456 | 438
OPEB [Member] | Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 427 | 411
OPEB [Member] | Pooled Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 607 | 697
OPEB [Member] | Pooled Funds [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 569 | 653
OPEB [Member] | Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 607 | 697
OPEB [Member] | Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Consumers Energy Company [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | $ 569 | $ 653

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