Fair Value Measurements - Reconciles Net Loss to Unrealized Loss on Equity Securities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Net gain (loss) recognized during the period on equity securities	$ 0	$ 767	$ (8,285)	$ 7,934
Less: Net gain (loss) recognized during the period on equity securities sold during the period	0	299	(8,285)	536
Unrealized gain recognized during the reporting period on equity securities still held at the reporting date	$ 0	$ 468	$ 0	$ 7,398