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Estimated future benefit payments and subsidies (Details 7) - Qualified Plan - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2022
Underfunded Plan | Pension Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year |  | $ 0
Defined Benefit Plan, Plan Assets, Additional Contributions by Employer | $ 20,000,000 |
2023 |  | 24,936,000
2024 |  | 24,882,000
2025 |  | 24,749,000
2026 |  | 24,605,000
2027 |  | 24,387,000
2028-2032 |  | 114,850,000
Overfunded Plan | Other Postretirement Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year |  | 595,000
2023 |  | 4,275,000
2024 |  | 4,371,000
2025 |  | 4,456,000
2026 |  | 4,509,000
2027 |  | 4,523,000
2028-2032 |  | 16,917,000
2023 |  | 62,000
2024 |  | 53,000
2025 |  | 46,000
2026 |  | 39,000
2027 |  | 31,000
2028-2032 |  | $ 93,000

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