CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue:
Revenue	$ 20,624	$ 19,241	$ 211,064	$ 54,670
Expenses:
Cost of sales - intangible asset amortization	1,434	701	4,256	701
Research and development	24,797	29,381	144,687	96,808
Selling, general and administrative	34,905	45,924	130,247	107,676
Total expenses	53,214	84,249	256,153	213,428
Loss from operations	(32,590)	(65,008)	(45,089)	(158,758)
Other income (expense):
Investment income	1,487	1,675	4,282	4,089
Other (expense)	(136)	(25)	(276)	(148)
Loss before income tax expense	(31,239)	(63,358)	(41,083)	(154,817)
Income tax expense	(259)	(233)	(551)	(447)
Net loss	(31,498)	(63,591)	(41,634)	(155,264)
Ionis [Member]
Expenses:
Net loss share from commercial activities under arrangement with Ionis Pharmaceuticals, Inc.	(8,889)		(29,410)
Common Stock [Member] | Ionis [Member]
Other income (expense):
Net loss	$ (23,772)	$ (47,789)	$ (28,174)	$ (110,882)
Net loss per share, basic and diluted (in dollars per share)	$ (0.34)	$ (0.73)	$ (0.40)	$ (1.93)
Weighted-average shares outstanding, basic and diluted (in shares)	70,221,338	65,538,467	69,680,886	57,346,539
Common Stock [Member] | Others [Member]
Other income (expense):
Net loss per share, basic and diluted (in dollars per share)	$ (0.34)	$ (0.73)	$ (0.60)	$ (2.07)
Weighted-average shares outstanding, basic and diluted (in shares)	22,821,555	21,671,415	22,509,819	21,446,813
Product [Member]
Revenue:
Revenue	$ 11,944		$ 28,563
Expenses:
Cost of sales	967	$ 1,043	3,373	$ 1,043
Licensing [Member]
Revenue:
Revenue	136	12,000	6,172	12,000
Expenses:
Cost of sales		7,200	3,000	7,200
Research and Development and License Revenue Under Collaborative Agreement [Member]
Revenue:
Revenue	$ 8,544	$ 7,241	$ 176,329	$ 42,670