Commitments And Contingencies (Reconciliation Of Contingent Consideration Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Contingent Consideration, Reconciliation of Change in Liability
Balance at beginning of period	$ 9,241	$ 10,840	$ 8,129
Acquisitions	7,288	1,322	4,766
Payments	(7,682)	(4,944)	(3,974)
Accretion	1,652	1,274	1,196
Fair value adjustments	1,257	749	723
Balance at end of the period	12,545	9,241	10,840
Contingent consideration, fair value	9,241	10,840	8,129	$ 12,545	$ 9,241	$ 10,840
Less current portion in accrued expenses and other current liabilities				(4,658)	(5,829)	(3,877)
Total long-term portion in other long-term liabilities				7,887	$ 3,412	$ 6,963
Contingent consideration, total remaining estimated payments				$ 15,300
Business Acquisition, Contingent Consideration, Net Foreign Currency Translation Adjustment	$ 789	$ 0	$ 0