Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) [Abstract]
General and administrative expense	$ (1,715)	$ (1,794)	$ (5,109)	$ (5,339)
Operating income (loss)	(1,715)	(1,794)	(5,109)	(5,339)
Interest and investment income	1,263	728	3,340	1,754
Interest expense	(6)	(11)	(17)	(22)
Other expense	(1,749)	(1,206)	(2,937)	(3,519)
Income (loss) from continuing operations before income taxes and equity in net income (loss) of affiliates	(2,207)	(2,283)	(4,723)	(7,126)
Income tax (provision) benefit	(6,669)	(16,552)	(1,014)	(82,236)
Income (loss) from continuing operations before equity in net income (loss) of affiliates	(8,876)	(18,835)	(5,737)	(89,362)
Equity in net income (loss) of affiliates	55,095	43,372	56,734	183,086
(Loss) income from continuing operations	46,219	24,537	50,997	93,724
Income (loss) from discontinued operations, net of tax provision	(25)		(62)	(5)
Net (loss) income	46,194	24,537	50,935	93,719
Other comprehensive income (loss), net of tax	(5,410)	(12,356)	2,362	(15,215)
Comprehensive income (loss)	$ 40,784	$ 12,181	$ 53,297	$ 78,504
Net income (loss) per share: Basic
(Loss) income from continuing operations	$ 1.49	$ 0.79	$ 1.65	$ 3.03
Income (loss) from discontinued operations, net of tax
Net (loss) income	1.49	0.79	1.65	3.03
Net income (loss) per share: Diluted
(Loss) income from continuing operations	1.48	0.77	1.63	2.98
Income (loss) from discontinued operations, net of tax
Net (loss) income	$ 1.48	$ 0.77	$ 1.63	$ 2.98
Weighted average common shares outstanding:
Basic	30,933	30,933	30,933	30,933
Diluted	31,008	31,008	31,008	31,008