Summary of Significant Accounting Policies - Marketable Equity Securities (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary of Significant Accounting Policies
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
Unrealized loss (gain) on marketable equity security		$ 3,000	$ 2,400	$ (2,375)	$ 18,913