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

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-Publisher FASB
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