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The license fee payment receivable per drug under the collaboration agreement.

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The maximum amount of payments receivable for commercialization milestones under the collaboration agreement.

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The maximum amount of payments receivable for development milestones under the collaboration agreement.

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The maximum amount of payments receivable for milestones under the collaboration agreement.

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The maximum amount of payments receivable for regulatory milestones under the collaboration agreement.

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The number of drugs with an exclusive option that could be exercised to develop and commercialize the drug and a license fee is paid under the collaboration agreement. The collaboration partner will assume all further global development, regulatory and commercialization activities for the licensed drug.

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The percentage of license fees, milestone payments and royalties paid as sublicense fee under the collaboration agreement.

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The amount of the upfront payment received during the period under the collaboration agreement that was paid as a sublicense fee.

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The amount of the upfront payment received during the period under the collaboration agreement that was retained by the entity.

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The potential premium received if common stock is purchased in the future under a Stock Purchase Agreement (SPA) in conjunction with the collaboration agreement.

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The total amount of the premium received over the trading price of common stock at the time of purchase.

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The cash inflow from the sale of common stock, including the premium paid for the purchase of common stock.

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The number of separate performance obligations under the collaboration agreement.

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The amount of consideration the Company is eligible to earn under the collaboration agreement, including any variable consideration.

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Royalty percentage received on the sales of a drug by a collaboration partner under the collaboration agreement.

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The amount of upfront payments received during the period under the collaboration agreement.

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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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Collaborative Arrangements and Licensing Agreements, Novartis (Details) $ in Thousands, shares in Millions	1 Months Ended		3 Months Ended			9 Months Ended
	Jul. 31, 2017 USD ($)	Jan. 31, 2017 Drug	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) PerformanceObligation shares	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangement and Licensing Agreement [Abstract]
Proceeds from sale of common stock to Novartis in a private placement						$ 0	$ 50,000
Revenue			$ 145,395	$ 118,314		407,559	346,387
Deferred revenue								$ 233,362
R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue			62,639	$ 83,697		225,584	$ 280,281
Novartis [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Shares issued (in shares) \| shares					1.6
Proceeds from sale of common stock					$ 100,000
Number of separate performance obligations \| PerformanceObligation					4
Transaction price					$ 108,400
Premium received on shares issued					28,400
Potential premium received if common stock is purchased in the future					5,000
Deferred revenue			$ 34,800			$ 34,800		$ 70,700
Novartis [Member] \| Revenue [Member] \| Strategic Partner [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Concentration percentage			5.00%	8.00%		10.00%	6.00%
Novartis [Member] \| Minimum [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of drugs with exclusive option that could be exercised \| Drug		1
Novartis [Member] \| R&D Services for AKCEA-APO(a)-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price					64,000
Novartis [Member] \| Delivery of AKCEA-APO(a)-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price					1,500
Novartis [Member] \| R&D Services for AKCEA-APOCIII-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price					40,100
Novartis [Member] \| Delivery of AKCEA-APOCIII-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Transaction price					2,800
Novartis [Member] \| R&D [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue			$ 7,200	$ 9,900		$ 42,700	$ 21,700
Akcea [Member] \| Novartis [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Upfront payment received					75,000
Portion of upfront payment retained					60,000
Portion of upfront payment paid as a sublicense fee					$ 15,000
License fee receivable per drug			150,000			$ 150,000
Percentage of license fees, milestone payments and royalties paid as sublicense fee						50.00%
Proceeds from sale of common stock to Novartis in a private placement	$ 50,000
Akcea [Member] \| Novartis [Member] \| AKCEA-APO(a)-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable for milestones			600,000			$ 600,000
Maximum amount of payments receivable for development milestones			25,000			25,000
Maximum amount of payments receivable for regulatory milestones			290,000			290,000
Maximum amount of payments receivable for commercialization milestones			285,000			$ 285,000
Royalty percentage received on sales of drug						20.00%
Akcea [Member] \| Novartis [Member] \| AKCEA-APOCIII-L [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable for milestones			530,000			$ 530,000
Maximum amount of payments receivable for development milestones			25,000			25,000
Maximum amount of payments receivable for regulatory milestones			240,000			240,000
Maximum amount of payments receivable for commercialization milestones			$ 265,000			$ 265,000
Royalty percentage received on sales of drug						20.00%