Acquisitions (Schedule of Contingent Consideration Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Acquisitions [Abstract]
Beginning Balance	$ 2,211
Net decrease in estimated fair value of contingent consideration included in Administrative expenses	(2,211)	$ (3,789)
Ending Balance		$ 2,211