Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Significant components of deferred tax assets and liabilities
Post-retirement benefits	$ 976	$ 947
Inventory reserves	1,323	1,361
Loss carry-forwards	3,911	4,547
Credit carry-forwards	13,415	10,467
Accrued expenses	4,852	4,543
Research and development expenditures	18,980	19,448
Operating lease liabilities	6,715	5,865
Stock compensation	2,371	2,426
Foreign exchange loss	2,010	2,075
Other	762	835
Gross deferred tax assets	55,315	52,514
Depreciation and amortization	23,349	23,067
Statutory inventory adjustments	1,359	1,110
Qualified replacement plan	3,080	3,507
Operating lease assets	6,355	5,531
Subsidiaries' unremitted earnings	1,599	2,562
Other	749	900
Gross deferred tax liabilities	36,491	36,677
Net deferred tax assets	18,824	15,837
Deferred tax asset valuation allowance	(8,370)	(8,386)
Total net deferred tax assets	$ 10,454	$ 7,451