Organization and Significant Accounting Policies, Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Loss [Roll Forward]
Balance		$ 1,684,547	$ 1,187,160	$ 365,280
Adjustments to other comprehensive loss from purchase of noncontrolling interest of Akcea Therapeutics, Inc.		(127)	0	0
Net other comprehensive loss for the period		4,219	6,726	(257)
Balance		843,347	1,684,547	1,187,160
Income tax expense (benefit) included in other comprehensive loss		0	(1,400)	(300)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance		(25,290)	(32,016)	(31,759)
Balance		(21,071)	(25,290)	(32,016)
Unrealized Gains (Losses) on Securities [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Other comprehensive loss before reclassifications, net of tax	[1]	3,729	6,633	(280)
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Other comprehensive loss before reclassifications, net of tax		$ 617	$ 93	$ 23

[1] We did not have tax expense included in our other comprehensive loss for the year ended December 31, 2020. For the years ended December 31, 2019 and 2018, we had a tax benefit $1.4 million and $0.3 million included in other comprehensive loss respectively.