Consolidated Statements of Operations - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Contract revenue - related party	$ 0	$ 616,000	$ 1,057,000
Total revenue	0	616,000	1,057,000
Operating expenses
Research and development	84,575,000	62,288,000	29,092,000
General and administrative	30,852,000	16,700,000	13,934,000
Total operating expenses	115,427,000	78,988,000	43,026,000
Loss from operations	(115,427,000)	(78,372,000)	(41,969,000)
Other income, net	624,000	187,000	57,000
Net loss	(114,803,000)	(78,185,000)	(41,912,000)
Net loss attributable to common shareholders	$ (114,803,000)	$ (78,185,000)	$ (41,912,000)
Basic and diluted net loss per share (usd per share)	$ (5.41)	$ (4.54)	$ (2.68)
Weighted-average common shares outstanding - basic and diluted (in shares)	21,215	17,228	15,651