Benefit Plans and Other Postretirement Benefits - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) benefitPlan	Dec. 31, 2019 USD ($)
Benefit Plans and Other Postretirement Benefits
Number of qualified pension plans \| benefitPlan	2
Pension Benefits
Benefit Plans and Other Postretirement Benefits
Expects to contribute to the pension plans	$ 30
Actuarial loss	126	$ 207
GenOn \| Restructuring Support Agreement
Benefit Plans and Other Postretirement Benefits
Expects to contribute to the pension plans	$ 14

Number Of Defined Benefit Plans

No definition available.

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- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

+ References

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921

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- Details

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- Details

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