Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details 3) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Significant components of deferred tax assets and liabilities
Post-retirement benefits	$ 1,100	$ 1,061
Inventory reserves	708	1,236
Loss carry-forwards	4,724	4,647
Credit carry-forwards	15,964	16,909
Accrued expenses	4,932	5,685
Research expenditures	17,953	16,847
Deferred Tax Assets, Leasing Arrangements	6,211	0
Stock compensation	2,232	2,142
Foreign exchange loss	1,986	2,245
Other	230	207
Gross deferred tax assets	56,040	50,979
Depreciation and amortization	12,453	11,500
Pensions	13,552	11,736
Deferred Tax Liabilities, Leasing Arrangements	5,963	0
Subsidiaries' unremitted earnings	1,903	1,258
Gross deferred tax liabilities	33,871	24,494
Net deferred tax assets	22,169	26,485
Deferred tax asset valuation allowance	(8,011)	(8,274)
Total net deferred tax assets	$ 14,158	$ 18,211