Goodwill and Acquired Intangible Assets, Net (Tables)

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets and Goodwill [Table Text Block]

A summary of acquired intangible assets and goodwill activity for the nine months ended September 30, 2018 is presented below:

(in thousands)	Acquired Intangible Assets			Goodwill			Total Intangible Assets
Balance as of December 31, 2017	$	150,543		$	717,386		$	867,929
Increases (decreases):
Acquisitions	—			20,742			20,742
Amortization	(17,179		)	—			(17,179		)
Other (primarily changes in foreign currency exchange rates)	(4,778		)	(22,383		)	(27,161		)
Balance as of September 30, 2018	$	128,586		$	715,745		$	844,331