Goodwill and Intangible Assets, Goodwill) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Balance at beginning of period	$ 305,238
Preliminary purchase price allocations for acquisition	10,467
Effect of foreign currency translation adjustments	(300)
Balance at end of period	$ 315,405