Marketable Securities (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Number	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-For-Sale Securities Number of Securities Owned | Number	7
Available-For-Sale Securities Number Of Securities Owned Unrealized Losses | Number	7
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | $	$ 5	$ 17
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | $	$ 100