Fair Value Measurements - Summary of Level 3 Investments (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Dividend income from investments in preferred stock		$ 0	$ 48	$ 14,841
Proceeds from sales of equity securities	$ (21,587)	0	(23,456)	(217)
Significant Unobservable Inputs (Level 3)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 0	191
Retained interest in deconsolidated subsidiary			14,239
Dividend income from investments in preferred stock			48
Net unrealized appreciation in the fair value of the investments in equity securities and preferred stock			7,446
Proceeds from sales of equity securities			(21,587)
Proceeds to be received from preferred stock			(337)
Ending balance			$ 0	$ 191