Goodwill and Acquired Intangible Assets - Schedule of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Schedule of Goodwill [Roll Forward]
Balance as of January 1, 2018	$ 1,498,688
Measurement period adjustments	(2,263)
Foreign currency translation	2,481
Balance as of March 31, 2018	$ 1,498,906