CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
General and administrative expense	$ 5,148	$ 4,486	$ 10,738	$ 9,433
Operating loss	(5,148)	(4,486)	(10,738)	(9,433)
Other income (loss)	(2,452)	(89)	(3,887)	160
Interest income	666	1,087	1,465	1,888
Interest expense	(3,422)	(2,112)	(6,112)	(3,310)
Equity loss	(14,540)	(23,497)	(11,794)	(40,499)
Net loss before income taxes	(24,896)	(29,097)	(31,066)	(51,194)
Income tax benefit (expense)	0	0	0	0
Net loss	$ (24,896)	$ (29,097)	$ (31,066)	$ (51,194)
Net loss per share:
Basic (in dollars per share)	$ (1.21)	$ (1.43)	$ (1.51)	$ (2.51)
Diluted (in dollars per share)	$ (1.21)	$ (1.43)	$ (1.51)	$ (2.51)
Weighted average shares used in computing loss per share:
Basic (in shares)	20,539	20,411	20,523	20,395
Diluted (in shares)	20,539	20,411	20,523	20,395