Revenue from Collaboration and License Agreements - Summary of Net Revenue from Partners in Connection with Collaboration and License Agreements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 16,074	$ 163,816
Licensing Revenue and Research and Development and License Revenue Under Collaborative Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	915	157,062
Licensing Revenue and Research and Development and License Revenue Under Collaborative Agreement [Member] | Strategic Collaboration with Novartis [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	311	$ 157,062
Licensing Revenue and Research and Development and License Revenue Under Collaborative Agreement [Member] | Vupanorsen (AKCEA-ANGPTL3-LRx) License Agreement with Pfizer [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 604