Goodwill and Intangible Assets - Changes in Goodwill (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Beginning Balance, Goodwill Net	$ 302,517	$ 269,265
Acquisition-Related	167
Acquisition-Related		38,536
Effect of Foreign Currency	1,236	(5,284)
Ending Balance, Goodwill Net	303,920	302,517
Americas [Member]
Goodwill [Line Items]
Beginning Balance, Goodwill Net	255,436	258,496
Acquisition-Related	291
Acquisition-Related		2,175
Effect of Foreign Currency	953	(5,235)
Ending Balance, Goodwill Net	256,680	255,436
EMEA [Member]
Goodwill [Line Items]
Beginning Balance, Goodwill Net	47,081	10,769
Acquisition-Related	(124)
Acquisition-Related		36,361
Effect of Foreign Currency	283	(49)
Ending Balance, Goodwill Net	$ 47,240	$ 47,081

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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