Fair value - pension (Details 8) - Qualified Plan - Underfunded Plan - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 270,462	$ 373,109	$ 383,834
Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 8,170	4,637
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	7.00%
Pension investments in insurance contracts	100.00%
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 7,388	7,483
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 467	$ 1,279
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	16.00%	19.00%
Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 154,443	$ 208,476
Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 81,363	$ 125,167
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	29.00%	37.00%
Municipal bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 5,904	$ 7,507
U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 3,924	$ 9,015
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	7.00%	9.00%
Pooled Separate Accounts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 3,241	$ 3,088
Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 270,462	$ 373,109
Defined Benefit Plan, Equity Securities, US, Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	24.00%	16.00%
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	17.00%	19.00%
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 7,388	$ 7,483
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	121,072	167,093
Quoted Prices in Active Markets for Identical Assets  (Level 1) | U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	3,044	7,113
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	131,504	181,689
Significant Other Observable Inputs  (Level 2) | Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	8,170	4,637
Significant Other Observable Inputs  (Level 2) | Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	467	1,279
Significant Other Observable Inputs  (Level 2) | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	33,371	41,383
Significant Other Observable Inputs  (Level 2) | Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	81,363	125,167
Significant Other Observable Inputs  (Level 2) | Municipal bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	5,904	7,507
Significant Other Observable Inputs  (Level 2) | U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	880	1,902
Significant Other Observable Inputs  (Level 2) | Pooled Separate Accounts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	3,241	3,088
Significant Other Observable Inputs  (Level 2) | Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	133,396	184,963
Fair Value Measured at Net Asset Value Per Share | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 5,562	$ 6,457