Cash and Cash Equivalents and Investments in Marketable Securities (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Investment Income, Interest	$ 527	$ 768	$ 602	$ 1,730
Maximum term to maturity from date of purchase (years)	1 year
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment Income, Interest	$ 100	$ 500	$ 100	$ 900