Summary of Significant Accounting Policies - Marketable Equity Securities (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Unrealized loss (gain) on marketable equity security			$ 577	$ 46,492	$ 1,631
Proceeds from sale of marketable equity security	$ 70,000		70,019	0	0
Gain on sale of mark to market valuation		$ 17,900	17,883
Interest and other income (expense),
Summary Of Significant Accounting Policies [Line Items]
Unrealized loss (gain) on marketable equity security			$ 600	$ 46,500	$ 1,600