Other Income (Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
Interest and investment income	$ 696	$ 238	$ 548
Income tax expense	(819)	(327)	(214)
Other non-operating income	1	4	0
Total other income (expense)	$ (122)	$ (85)	$ 334