Fair value - other postretirement (Details 9) - Other Postretirement Benefits - Qualified Plan - Overfunded Plan - 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	$ 76,326	$ 100,158	$ 101,639
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	$ 4,196	4,281
Postretirement Investments in Collective and Mutual Funds	7.00%
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 2,572	2,332
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		$ 1
Postretirement Investments in Collective and Mutual Funds	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	$ 10	$ 94
Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	69,548	93,447
Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 76,326	$ 100,158
Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	29.00%	37.00%
Postretirement Investments in Insurance Contracts	69.00%	58.00%
Defined Benefit Plan, Equity Securities, US, Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	24.00%	16.00%
Postretirement Investments in Insurance Contracts	14.00%	13.00%
Defined Benefit Plan, Equity Securities, US, Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Insurance Contracts	4.00%	5.00%
U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	7.00%	9.00%
Postretirement Investments in Insurance Contracts	13.00%	13.00%
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	17.00%	19.00%
Postretirement Investments in Insurance Contracts		11.00%
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	$ 2,572	$ 2,332
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	5	4
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	2,577	2,336
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	4,196	4,281
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		1
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	5	90
Significant Other Observable Inputs  (Level 2) | Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	69,548	93,447
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	$ 73,749	97,819
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		$ 3