Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Operations [Abstract]
General and administrative expenses	$ (6,717)	$ (6,612)
Recovery of affiliate doubtful receivable	5,854	0
Operating income (loss)	(863)	(6,612)
Interest and investment income	1,050	5,727
Interest expense	(26)	(24)
Other expense	(10,898)	(4,586)
Income (loss) before income taxes and equity in net income (loss) of affiliates	(10,737)	(5,495)
Income tax (provision) benefit	(12,886)	(6,153)
Income (loss) before equity in net income (loss) of affiliates	(23,623)	(11,648)
Equity in net income (loss) of affiliates	116,716	101,403
Net income	$ 93,093	$ 89,755
Net income per share:
Basic	$ 3.01	$ 2.90
Diluted	$ 2.98	$ 2.88
Weighted average common shares outstanding:
Basic	30,933	30,933
Diluted	31,020	31,008