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Cumulative amount of payments received under the collaboration agreement as of the end of the reporting period.

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The next potential payment to be earned under the collaboration agreement.

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No definition available.

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The number of medicines currently being developed under the collaboration agreement(s).

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Collaborative Arrangements and Licensing Agreements, Biogen (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021 USD ($) Medicine	Jun. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Medicine	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue	$ 133,093		$ 160,079	$ 370,450	$ 438,983
SPINRAZA Royalties [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue	66,572		74,171	198,726	211,925
R&D Revenue [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue	$ 48,273		64,739	$ 115,321	169,948
Biogen [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of medicines currently being developed \| Medicine	8			8
Revenue	$ 84,000		$ 125,400	$ 262,100	$ 310,500
Deferred revenue	$ 412,500			$ 412,500		$ 465,800
Biogen [Member] \| Revenue [Member] \| Strategic Partner [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Concentration percentage	63.00%		78.00%	71.00%	71.00%
Biogen [Member] \| SPINRAZA Royalties [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue	$ 66,600		$ 74,200	$ 198,700	$ 211,900
Biogen [Member] \| R&D Revenue [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue	17,400		$ 51,200	63,400	$ 98,600
Biogen [Member] \| Minimum [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Cumulative payments received	3,000,000			3,000,000
2013 Strategic Neurology [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Next prospective payment	$ 8,000			$ 8,000
2013 Strategic Neurology [Member] \| ION541 [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue		$ 10,000