Marketable Securities Textual (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Marketable Securities [Abstract]
Interest Income, Money Market Deposits	$ 2	$ 25	$ 17	$ 86