Milestone payment which the entity is obliged to pay upon regulatory approval

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Amount of cash outflow for milestone obligations paid.

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Upfront Licensing Fee

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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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The amount of identifiable intangible assets recognized as of the acquisition date.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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No definition available.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Remaining amortization period of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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 increase (decrease) 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 increase (decrease) of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

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Amount of increase in assets, excluding financial assets and goodwill, lacking physical substance with an indefinite life, from an acquisition.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Intangible assets and goodwill - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	25 Months Ended
	Dec. 31, 2019	May 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Sep. 30, 2020	Apr. 20, 2017
Finite-Lived Intangible Assets [Line Items]
Useful life					7 years
Amortization of acquired intangible assets			$ 9,630	$ 7,025	$ 26,309	$ 19,677
Total allocation of IPR&D assets					576,500
Change in indefinite-lived intangibles								$ 0
Goodwill	$ 82,341		82,341		82,341		$ 82,341	$ 82,341
Research and development			92,998	$ 63,076	359,630	175,621
Changes in goodwill			$ 0		$ 0
Weighted Average
Finite-Lived Intangible Assets [Line Items]
Remaining amortization period					3 years 8 months 12 days
Akcea
Finite-Lived Intangible Assets [Line Items]
Upfront licensing fee					$ 12,000
Non-collaborative Arrangement Transactions \| Akcea
Finite-Lived Intangible Assets [Line Items]
Milestone payments	$ 4,000	$ 6,000			$ 4,000		$ 6,000
Useful life					10 years
Emflaza asset acquisition
Finite-Lived Intangible Assets [Line Items]
Finite-Lived intangibles									$ 148,400
Milestone obligation payments made					$ 13,800	$ 7,400