Summary of Significant Accounting Policies - Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Restricted assets	$ 1,604	$ 25,907
Prepaid pension costs	39,951	38,100
Other assets	37,704	31,310
Total other assets	$ 79,259	$ 95,317