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Estimated future benefit payments and subsidies (Details 7) - Qualified Plan - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2021
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 |
2022 |  | 24,644,000
2023 |  | 24,766,000
2024 |  | 24,897,000
2025 |  | 24,739,000
2026 |  | 24,571,000
2027-2031 |  | 117,413,000
Overfunded Plan | Other Postretirement Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year |  | 601,000
2022 |  | 4,393,000
2023 |  | 4,522,000
2024 |  | 4,572,000
2025 |  | 4,612,000
2026 |  | 4,642,000
2027-2031 |  | 17,867,000
2022 |  | 70,000
2023 |  | 65,000
2024 |  | 58,000
2025 |  | 52,000
2026 |  | 46,000
2027-2031 |  | $ 157,000

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