CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
General and administrative expense	$ 4,486	$ 4,849	$ 9,433	$ 10,077
Operating loss	(4,486)	(4,849)	(9,433)	(10,077)
Other income (loss), net	(89)	659	160	659
Interest income	1,087	527	1,888	947
Interest expense	(2,112)	(1,155)	(3,310)	(2,304)
Equity income (loss)	(23,497)	43,794	(40,499)	34,299
Net income (loss) before income taxes	(29,097)	38,976	(51,194)	23,524
Income tax benefit (expense)	0	0	0	0
Net income (loss)	$ (29,097)	$ 38,976	$ (51,194)	$ 23,524
Net income (loss) per share:
Basic (in dollars per share)	$ (1.43)	$ 1.92	$ (2.51)	$ 1.15
Diluted (in dollars per share)	$ (1.43)	$ 1.70	$ (2.51)	$ 1.09
Weighted average shares used in computing income (loss) per share:
Basic (in shares)	20,411	20,333	20,395	20,391
Diluted (in shares)	20,411	23,539	20,395	23,602