Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) [Abstract]
General and administrative expenses	$ (2,015)	$ (1,709)	$ (6,000)	$ (4,900)
Operating income (loss)	(2,015)	(1,709)	(6,000)	(4,900)
Interest and investment income	728	44	1,754	140
Interest expense	(11)	(6)	(22)	(15)
Other income (expense)	(985)	(187)	(2,858)	(1,306)
Income (loss) from continuing operations before income taxes and equity in net income (loss) of affiliates	(2,283)	(1,858)	(7,126)	(6,081)
Income tax (provision) benefit	(16,552)	(8,911)	(82,236)	(31,066)
Income (loss) from continuing operations before equity in net income (loss) of affiliates	(18,835)	(10,769)	(89,362)	(37,147)
Equity in net income (loss) of affiliates	43,372	6,948	183,086	96,799
(Loss) income from continuing operations	24,537	(3,821)	93,724	59,652
Income (loss) from discontinued operations, net of tax provision		(71)	(5)	(306)
Net (loss) income	24,537	(3,892)	93,719	59,346
Other comprehensive income (loss), net of tax	(12,356)	1,713	(15,215)	11,289
Comprehensive income (loss)	$ 12,181	$ (2,179)	$ 78,504	$ 70,635
Net income (loss) per share: Basic
(Loss) income from continuing operations	$ 0.79	$ (0.12)	$ 3.03	$ 1.93
Income (loss) from discontinued operations, net of tax				(0.01)
Net (loss) income	0.79	(0.12)	3.03	1.92
Net income (loss) per share: Diluted
(Loss) income from continuing operations	0.77	(0.12)	2.98	1.85
Income (loss) from discontinued operations, net of tax				(0.01)
Net (loss) income	$ 0.77	$ (0.12)	$ 2.98	$ 1.84
Weighted average common shares outstanding:
Basic	30,933	30,933	30,933	30,933
Diluted	31,008	30,933	31,008	31,008