Postretirement Benefits - Other Comprehensive Loss (Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amounts recognized in other comprehensive loss (income)
Net actuarial loss (gain) arising during the year	$ 28,279	$ (89,768)	$ (75,091)
Amortization of net actuarial gain (loss)	15,331	(7,320)	(16,106)
Amortization of prior service cost	(1,446)	(1,443)	(1,428)
Plan amendments	583	1,620	4,059
Total recognized in other comprehensive loss (income)	$ 42,747	$ (96,911)	$ (88,566)