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Contingencies and Commitments (Guarantees) (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 | Jul. 31, 2020
Variable Interest Entity, Primary Beneficiary | Aviator Wind Class B Membership |  |
Guarantees And Other Contingencies [Line Items] |  |
Ownership percentage |  | 49.00%
Guarantees |  |
Guarantees And Other Contingencies [Line Items] |  |
Expiration Date | indefinite |
Maximum Obligation | $ 30 |
Carrying Amount | $ 0 |
Guarantees | Consumers Energy Company |  |
Guarantees And Other Contingencies [Line Items] |  |
Expiration Date | indefinite |
Maximum Obligation | $ 30 |
Carrying Amount | $ 0 |
Indemnification Agreement From Purchase Of Variable Interest Entity |  |
Guarantees And Other Contingencies [Line Items] |  |
Expiration Date | indefinite |
Maximum Obligation | $ 341 |
Carrying Amount | $ 0 |
Indemnity Obligations From Stock And Asset Sales Agreements |  |
Guarantees And Other Contingencies [Line Items] |  |
Expiration Date | indefinite |
Maximum Obligation | $ 153 |
Carrying Amount | 2 |
Tax And Other Indemnity Obligations | Consumers Energy Company |  |
Guarantees And Other Contingencies [Line Items] |  |
Carrying Amount | $ 1 |

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- Definition Guarantees And Other Contingencies [Line Items] + References No definition available. + Details
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- Definition The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248 + Details
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- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248 + Details
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- Definition Describe the approximate term of the guarantee or each group of similar guarantees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248 + Details
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