CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
General and administrative expense	$ 3,516	$ 3,758	$ 14,253	$ 13,191
Operating loss	(3,516)	(3,758)	(14,253)	(13,191)
Other loss	(1,078)	(379)	(4,965)	(219)
Interest income	718	1,004	2,182	2,892
Interest expense	(3,310)	(2,643)	(9,422)	(5,953)
Equity income (loss)	39,246	(12,874)	27,452	(53,373)
Net income (loss) before income taxes	32,060	(18,650)	994	(69,844)
Income tax benefit (expense)	0	0	0	0
Net income (loss)	$ 32,060	$ (18,650)	$ 994	$ (69,844)
Net income (loss) per share:
Basic (in dollars per share)	$ 1.56	$ (0.91)	$ 0.05	$ (3.42)
Diluted (in dollars per share)	$ 1.56	$ (0.91)	$ 0.05	$ (3.42)
Weighted average shares used in computing income (loss) per share:
Basic (in shares)	20,561	20,455	20,535	20,416
Diluted (in shares)	20,561	20,455	20,535	20,416