Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Goodwill [Roll Forward]
Goodwill balance at January 1	$ 335,433
Effect of foreign exchange	(181)
Additions and adjustments as the result of acquisitions	16,881
Goodwill balance at June 30	$ 352,133