Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Inventories
Finished goods	$ 11,057	$ 14,344
Work-in-process	13,679	15,629
Raw materials and purchased parts	107,056	108,381
Stores and supplies	48,756	44,705
Total inventories	180,548	183,059
Valued at lower of cost or market:
LIFO basis	92,939	96,680
FIFO basis	22,306	19,761
Average cost basis	65,303	66,618
Total inventories	180,548	183,059
Excess of inventories valued at current costs over LIFO	24,000	21,000
Change in income as a result of LIFO basis inventory valuation over FIFO basis valuation	$ 0	$ 2,600	$ 0