Other Non-Operating Income (Expense), Net (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Non-Operating Income (Expense), Net [Abstract]
Interest and dividend income		$ 109	$ 97	$ 80
Equity income (loss) from joint ventures		820	2,865	(768)	[1]
Gain (loss) on foreign exchange		(350)	(502)	(120)
Postretirement plan net periodic benefit credit (cost)		27	25	262
Other non-operating income, net		206	102	135
Total other non-operating income (expense), net		$ 812	$ 2,587	(411)
Orange Electronic Co., Ltd [Member]
Asset Impairment Charges [Abstract]
Impairment charges	$ 1,700			$ 1,700

[1] Year ended December 31, 2018 includes a noncash impairment charge of approximately $1.7 million related to our minority interest investment in Orange Electronic Co., Ltd.  See Note 9, “Investments in Unconsolidated Affiliates” for additional information.