Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Consolidated Statements of Operations [Abstract]
General and administrative expenses	$ (1,900)	$ (1,801)	$ (3,629)	$ (3,449)
Operating income (loss)	(1,900)	(1,801)	(3,629)	(3,449)
Interest and investment income	1	92	3	1,029
Interest expense	(5)	(6)	(11)	(11)
Other expense	(2,097)	(2,703)	(4,472)	(4,140)
Income (loss) before income taxes and equity in net income (loss) of affiliates	(4,001)	(4,418)	(8,109)	(6,571)
Income tax (provision) benefit	201	1,469	423	(647)
Income (loss) before equity in net income (loss) of affiliates	(3,800)	(2,949)	(7,686)	(7,218)
Equity in net income (loss) of affiliates	25,291	76,515	59,893	(40,559)
Net income (loss)	21,491	73,566	52,207	(47,777)
Other comprehensive income (loss), net of tax	(1,785)	(17,179)	(3,601)	14,111
Comprehensive income (loss)	$ 19,706	$ 56,387	$ 48,606	$ (33,666)
Net income per share:
Basic	$ 0.69	$ 2.38	$ 1.69	$ (1.54)
Diluted	$ 0.64	$ 2.36	$ 1.62	$ (1.54)
Weighted average common shares outstanding:
Basic	30,933	30,933	30,933	30,933
Diluted	31,032	31,017	31,032	30,933