Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) [Abstract]
General and administrative expenses	$ (1,922)	$ (1,674)	$ (3,985)	$ (3,191)
Operating income (loss)	(1,922)	(1,674)	(3,985)	(3,191)
Interest and investment income	627	48	1,026	96
Interest expense	(6)	(4)	(11)	(9)
Other income (expense)	(1,256)	(593)	(1,873)	(1,119)
Income (loss) from continuing operations before income taxes and equity in net income (loss) of affiliates	(2,557)	(2,223)	(4,843)	(4,223)
Income tax (provision) benefit	380	(8,480)	(65,684)	(22,155)
Income (loss) from continuing operations before equity in net income (loss) of affiliates	(2,177)	(10,703)	(70,527)	(26,378)
Equity in net income (loss) of affiliates		43,357	139,714	89,851
(Loss) income from continuing operations	(2,177)	32,654	69,187	63,473
Income (loss) from discontinued operations, net of tax provision		(102)	(5)	(235)
Net (loss) income	(2,177)	32,552	69,182	63,238
Other comprehensive income (loss), net of tax	179	417	(2,859)	9,576
Comprehensive income (loss)	$ (1,998)	$ 32,969	$ 66,323	$ 72,814
Net income (loss) per share: Basic
(Loss) income from continuing operations	$ (0.07)	$ 1.06	$ 2.24	$ 2.05
Income (loss) from discontinued operations, net of tax				(0.01)
Net (loss) income	(0.07)	1.06	2.24	2.04
Net income (loss) per share: Diluted
(Loss) income from continuing operations	(0.07)	1.03	2.21	1.98
Income (loss) from discontinued operations, net of tax				(0.01)
Net (loss) income	$ (0.07)	$ 1.03	$ 2.21	$ 1.97
Weighted average common shares outstanding:
Basic	30,933	30,933	30,933	30,933
Diluted	30,933	31,008	31,008	31,008