Organization and Significant Accounting Policies, Cash, Cash Equivalents and Investments (Details) $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($) Company	Jun. 30, 2020 USD ($)	Dec. 31, 2020 Investment Company	Dec. 31, 2020 USD ($) Company	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Cash, Cash Equivalents and Investments [Abstract]
Number of publicly held companies in which there is an equity ownership interest of less than 20% | Company	2		2	2
Number of privately held companies in which there is an equity ownership interest of less than 20% | Company	7		7	7
Number of investments in privately held companies that were revalued | Investment			3
Gain on investment				$ 16,540	$ 192	$ (210)
Dynacure SAS [Member]
Cash, Cash Equivalents and Investments [Abstract]
Gain on investment		$ 6,300
Suzhou-Ribo [Member]
Cash, Cash Equivalents and Investments [Abstract]
Gain on investment	$ 3,000
Aro Biotherapeutics [Member]
Cash, Cash Equivalents and Investments [Abstract]
Gain on investment	$ 5,500