Goodwill and Acquired Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 7,753	$ 6,598	$ 23,075	$ 20,025
Future amortization expense to be recognized in remainder of 2017	7,800		7,800
Future amortization expense 2018	31,400		31,400
Future amortization expense 2019	32,800		32,800
Future amortization expense 2020	29,500		29,500
Future amortization expense 2021	$ 24,100		$ 24,100