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Benefit Plans - Schedule of Net Benefit Costs (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Retirement Benefits [Abstract]        
Service cost $ 2,688 $ 2,337 $ 5,423 $ 4,780
Interest cost 2,530 2,816 5,110 5,720
Expected return on assets (4,742) (4,183) (9,494) (8,303)
Unrecognized actuarial loss 1,794 1,834 3,574 2,592
Amortization of prior service cost 13 (665) 25 76
Net periodic benefit cost $ 2,283 $ 2,139 $ 4,638 $ 4,865