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
-Subparagraph (a)(2)
-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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License rights and other intangible assets, net - Additional Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) Patent	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) Patent	Jun. 30, 2020 USD ($)	Dec. 31, 2020 Patent
Finite-Lived Intangible Assets [Line Items]
Number of issued patents \| Patent	83		83		77
License rights agreement [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets \| $	$ 0.8	$ 0.8	$ 1.5	$ 1.5
Domestic US Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Number of issued patents \| Patent	41		41		38
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets \| $	$ 0.1	$ 0.1	$ 0.2	$ 0.1