Schedule of Intangible Assets Recognized in Connection with Product Acquisitions (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Combinations [Abstract]
Beginning Balance	$ 180,950	$ 121,433	$ 129,160
Additions	16,429	68,327	224
Write offs			(78)
Impact of movement in exchange rates	(45)	(6)	69
Amortization expense	(10,751)	(8,804)	(7,942)
Ending Balance	186,583	180,950	$ 121,433
Goodwill at December 31, 2017	22,184
Net additions during fiscal 2018	3,606
Goodwill at December 31, 2018	25,790	22,184
Intangible assets and goodwill at Year End	$ 212,373	$ 203,134

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount of foreign currency translation gain (loss) which increases (decreases) assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

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