Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Inventories
Finished goods	$ 14,344	$ 16,171
Work-in-process	15,629	13,081
Raw materials and purchased parts	107,364	114,046
Stores and supplies	44,705	46,071
Total inventories	182,042	189,369
Valued at lower of cost or market:
LIFO basis	96,680	95,203
FIFO basis	18,747	18,685
Average cost basis	66,615	75,481
Total inventories	182,042	189,369
Excess of inventories valued at current costs over LIFO	21,000	32,000
Change in income as a result of LIFO basis inventory valuation over FIFO basis valuation	$ 2,600	$ 0	$ 0