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Benefit Plans and Other Postretirement Benefits - Expected Future Benefit Payments For the Next Five Years and Other (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
STP Defined Benefit Plans |  |  |
Curtailment gain |  |  | $ 8
Increase to pension liability |  |  | 32
Company's contributions to 401(k) plans |  |  |
Company contributions to defined contribution plans | $ 25 | $ 22 | 22
South Texas Project |  |  |
STP Defined Benefit Plans |  |  |
Amount reimbursed to STPNOC towards defined benefit plans | 17 | 8 |
Expected reimbursement of contribution to retirement plan obligations to STPNOC in 2014 | 13 |  |
Pension Benefit Payments |  |  |
NRG's expected future benefit payments |  |  |
2022 | 96 |  |
2023 | 94 |  |
2024 | 91 |  |
2025 | 87 |  |
2026 | 86 |  |
2027-2031 | 396 |  |
STP Defined Benefit Plans |  |  |
Curtailment gain | (2) | 0 | 0
Increase to pension liability | 0 | 0 |
Recognized amount in statement of financial position, statement of operations and accumulated OCI related to STP |  |  |
Funded status — STPNOC benefit plans | (116) | (217) |
Net periodic benefit credit | (27) | (8) | 0
Other changes in plan assets and benefit obligations recognized in other comprehensive income | (75) | (11) |
Pension Benefit Payments | South Texas Project |  |  |
Recognized amount in statement of financial position, statement of operations and accumulated OCI related to STP |  |  |
Funded status — STPNOC benefit plans | (50) | (99) |
Net periodic benefit credit | 17 | 7 |
Other changes in plan assets and benefit obligations recognized in other comprehensive income | (51) | 22 |
Other Postretirement Benefits Plan |  |  |
NRG's expected future benefit payments |  |  |
2022 | 7 |  |
2023 | 7 |  |
2024 | 7 |  |
2025 | 6 |  |
2026 | 6 |  |
2027-2031 | 26 |  |
Medicare prescription drug reimbursements |  |  |
2022 | 0 |  |
2023 | 0 |  |
2024 | 0 |  |
2025 | 0 |  |
2026 | 0 |  |
2027-2031 | 2 |  |
STP Defined Benefit Plans |  |  |
Curtailment gain | (1) | 0 | 0
Increase to pension liability | (1) | 0 |
Recognized amount in statement of financial position, statement of operations and accumulated OCI related to STP |  |  |
Funded status — STPNOC benefit plans | (105) | (90) |
Net periodic benefit credit | (6) | (10) | $ (9)
Other changes in plan assets and benefit obligations recognized in other comprehensive income | 9 | 13 |
Other Postretirement Benefits Plan | South Texas Project |  |  |
Recognized amount in statement of financial position, statement of operations and accumulated OCI related to STP |  |  |
Funded status — STPNOC benefit plans | (18) | (20) |
Net periodic benefit credit | (4) | (4) |
Other changes in plan assets and benefit obligations recognized in other comprehensive income | $ 4 | $ 5 |
South Texas Project |  |  |
STP Defined Benefit Plans |  |  |
Ownership interest in STP (as a percent) | 44.00% |  |
Percentage of contribution to the retirement plan obligation reimbursed | 44.00% |  |

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