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Retirement Benefits (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2023
Jul. 01, 2022
Jun. 30, 2023
Jul. 01, 2022
Pension        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 1,467 $ 1,964 $ 2,931 $ 4,134
Interest cost 3,798 2,766 7,575 5,504
Expected return on assets (3,980) (4,777) (7,955) (9,579)
Amortization and other 415 1,419 855 2,495
Net periodic benefit cost 1,700 1,372 3,406 2,554
Postretirement Medical        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 100 83 200 258
Interest cost 210 195 420 420
Amortization 90 (2) 180 173
Net periodic benefit cost $ 400 $ 276 $ 800 $ 851