Goodwill and Intangible Assets, Goodwill) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Goodwill and Intangible Assets [Abstract]
Balance at beginning of period	$ 275,205
Preliminary purchase price allocations for acquisitions	29,191
Effect of foreign currency translation adjustments	187
Balance at end of period	$ 304,583