Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) [Abstract]
General and administrative expenses	$ (1,636)	$ (1,865)
Operating income (loss)	(1,636)	(1,865)
Interest and investment income	888	399
Interest expense	(5)	(5)
Other expense	(634)	(815)
Income (loss) from continuing operations before income taxes and equity in net income (loss) of affiliates	(1,387)	(2,286)
Income tax (provision) benefit	587	(66,064)
Income (loss) from continuing operations before equity in net income (loss) of affiliates	(800)	(68,350)
Equity in net income (loss) of affiliates	5,094	139,714
(Loss) income from continuing operations	4,294	71,364
Income (loss) from discontinued operations, net of tax provision		(5)
Net (loss) income	4,294	71,359
Other comprehensive income (loss), net of tax	7,144	(3,038)
Comprehensive income (loss)	$ 11,438	$ 68,321
Net income (loss) per share: Basic
(Loss) income from continuing operations	$ 0.14	$ 2.31
Income (loss) from discontinued operations, net of tax
Net (loss) income	0.14	2.31
Net income (loss) per share: Diluted
(Loss) income from continuing operations	0.14	2.30
Income (loss) from discontinued operations, net of tax
Net (loss) income	$ 0.14	$ 2.30
Weighted average common shares outstanding:
Basic	30,933	30,933
Diluted	31,008	31,008