CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allocated share-based compensation expense	$ 79,167	$ 60,245	$ 131,770
Amortization of acquisition intangible assets	12,602	8,995	4,270
Cost of revenue
Allocated share-based compensation expense	4,450	3,658	8,931
Amortization of acquisition intangible assets	7,495	5,365	1,952
Research and development
Allocated share-based compensation expense	30,693	21,159	48,739
Sales and marketing
Allocated share-based compensation expense	19,707	11,950	19,046
Amortization of acquisition intangible assets	5,107	3,630	2,318
General and administrative
Allocated share-based compensation expense	$ 24,317	$ 23,478	$ 55,054

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

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