Consolidated Entities - ISP Fund LP (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	May 31, 2021	May 20, 2021	Dec. 31, 2020
CONSOLIDATED ENTITIES
Total assets	$ 887,239		$ 887,239				$ 999,570	[1]
Unrealized gain on equity investments			132,485	$ 39,245
Changes in fair values of equity and long-term investments	33,613	$ (29,368)	$ 133,973	$ 39,245
ISP Fund LP
CONSOLIDATED ENTITIES
Contributed to partnership for investing							300,000
Distribution from partnership					$ 110,000
Economic interest of the Partnership (in percent)			100.00%
Total assets	228,900		$ 228,900				$ 299,300
Investment-related expenses, net of investment-related income	200		1,500
Unrealized gain on equity investments	$ 10,100		30,600
Changes in fair values of equity and long-term investments			$ 10,500
Commitment for future contribution						$ 110,000
Lock-up period			36 months

[1] Consolidated balance sheet as of December 31, 2020 has been derived from audited consolidated financial statements.