Other Income (Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Income and Expenses [Abstract]
Interest and investment income	$ 436	$ 696	$ 238
Income tax expense	9	(819)	(327)
Other non-operating income	2	1	4
Total other income (expense)	$ 447	$ (122)	$ (85)