Condensed Consolidated Statements of Operations and Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Consolidated Statements of Operations and Comprehensive (loss) Income [Abstract]
General and administrative expenses	$ (1,801)	$ (1,697)	$ (3,449)	$ (3,500)
Operating income (loss)	(1,801)	(1,697)	(3,449)	(3,500)
Interest and investment income	92	1,566	1,029	3,168
Interest expense	(6)	(5)	(11)	(10)
Other expense	(2,703)	(755)	(4,140)	(1,971)
Income (loss) before income taxes and equity in net income (loss) of affiliates	(4,418)	(891)	(6,571)	(2,313)
Income tax (provision) benefit	1,469	(2,160)	(647)	(4,226)
Income (loss) before equity in net income (loss) of affiliates	(2,949)	(3,051)	(7,218)	(6,539)
Equity in net (loss) income of affiliates	76,515	41,278	(40,559)	83,282
Net (loss) income	73,566	38,227	(47,777)	76,743
Other comprehensive income (loss), net of tax	(17,179)	(6,646)	14,111	(13,052)
Comprehensive (loss) income	$ 56,387	$ 31,581	$ (33,666)	$ 63,691
Net (loss) income per share:
Basic	$ 2.38	$ 1.24	$ (1.54)	$ 2.48
Diluted	$ 2.36	$ 1.23	$ (1.54)	$ 2.46
Weighted average common shares outstanding:
Basic	30,933	30,933	30,933	30,933
Diluted	31,017	31,008	30,933	31,008