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Pension Plans and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2023
Sep. 30, 2022
Pension Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 3,098 $ 5,914 $ 11,092 $ 17,914
Interest cost 8,524 6,578 24,277 20,005
Expected return on plan assets (10,922) (10,950) (32,766) (32,851)
Amortization of prior service cost (credit) 123 75 369 225
Net loss (gain) recognition 1,184 997 3,208 3,084
Net periodic benefit cost 2,007 2,614 6,180 8,377
Other Postretirement Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 559 1,095 1,909 3,255
Interest cost 1,872 1,343 4,825 4,167
Expected return on plan assets (891) (700) (2,673) (2,100)
Amortization of prior service cost (credit) (263) (275) (789) (825)
Net loss (gain) recognition (54) 826 471 2,586
Net periodic benefit cost $ 1,223 $ 2,289 $ 3,743 $ 7,083