Summary of Significant Accounting Policies - Marketable Equity Securities (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
Unrealized loss (gain) on marketable equity security					$ 3,289	$ 34,931
Proceeds from sale of marketable equity security		$ 70,000		$ 0	70,019	0
Gain on sale of mark to market valuation	$ 17,900				17,883	0
Interest and other income (expense),
Summary Of Significant Accounting Policies [Line Items]
Unrealized loss (gain) on marketable equity security			$ 5,700	$ 16,800	$ 3,300	$ 35,500