Summary of Significant Accounting Policies (Schedule of Other, Net) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accounting Policies [Abstract]
Interest and dividend income	$ 3,208	$ 1,922
Net periodic benefit cost other than the service costs	(541)	(253)
Other expense	0	(23)
Other, net	$ 2,667	$ 1,646