Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Consolidated Statements of Operations [Abstract]
General and administrative expenses	$ (1,697)	$ (1,758)	$ (3,500)	$ (3,394)
Operating income (loss)	(1,697)	(1,758)	(3,500)	(3,394)
Interest and investment income	1,566	1,189	3,168	2,077
Interest expense	(5)	(6)	(10)	(11)
Other expense	(755)	(554)	(1,971)	(1,188)
Income (loss) before income taxes and equity in net income (loss) of affiliates	(891)	(1,129)	(2,313)	(2,516)
Income tax (provision) benefit	(2,160)	5,068	(4,226)	5,655
Income (loss) before equity in net income (loss) of affiliates	(3,051)	3,939	(6,539)	3,139
Equity in net income (loss) of affiliates	41,278	(3,455)	83,282	1,639
Income (loss) from continuing operations	38,227	484	76,743	4,778
Income (loss) from discontinued operations, net of tax		(37)		(37)
Net income (loss)	38,227	447	76,743	4,741
Other comprehensive (loss) income, net of tax	(6,646)	628	(13,052)	7,772
Comprehensive income (loss)	$ 31,581	$ 1,075	$ 63,691	$ 12,513
Basic
Income (loss) from continuing operations	$ 1.24	$ 0.02	$ 2.48	$ 0.15
Income (loss) from discontinued operations, net of tax
Net income (loss) per share	1.24	0.02	2.48	0.15
Diluted
Income (loss) from continuing operations	1.23	0.02	2.46	0.15
Income (loss) from discontinued operations, net of tax
Net income (loss) per share	$ 1.23	$ 0.02	$ 2.46	$ 0.15
Weighted average common shares outstanding:
Basic	30,933	30,933	30,933	30,933
Diluted	31,008	31,008	31,008	31,008