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Pensions (Details) - Pension Plans [Member] - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2023
Sep. 30, 2022
Dec. 31, 2022
Components of Net Periodic Pension Cost [Abstract]          
Service cost $ 150 $ 257 $ 449 $ 769  
Interest cost 469 334 1,407 1,002  
Expected return on plan assets (903) (1,054) (2,709) (3,163)  
Amortization of prior service cost (4) (4) (10) (10)  
Rate-regulated adjustment 677 1,042 2,154 3,127  
Net periodic pension expense 389 $ 575 1,291 $ 1,725  
Employer Contributions [Abstract]          
Estimated employer contributions in 2023         $ 1,680
Employer contributions made in 2023     1,291    
Estimated remaining employer contributions in 2023 $ 389   $ 389