Amount of liability, recognized in statement of financial position, for defined benefit pension plan. Excludes other postretirement benefit plan.

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Benefit Plans and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017
GenOn
Benefit Plans and Other Postretirement Benefits
Pension liability retained	$ 92
Liability retained other post-employment and retiree health and welfare benefits	25
Restructuring Support Agreement \| GenOn
Benefit Plans and Other Postretirement Benefits
Amount of pension liability future contributions			$ 13
Expects to contribute to the pension plans	13
Pension Benefits \| Scenario, Plan
Benefit Plans and Other Postretirement Benefits
Expects to contribute to the pension plans	41
Pension Benefits \| GenOn
Benefit Plans and Other Postretirement Benefits
Liability retained other post-employment and retiree health and welfare benefits	$ 0	$ 0