Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating expenses:
Research and development	$ 38,826	$ 39,165
General and administrative	20,876	22,697
Total operating expenses	59,702	61,862
Operating loss	(59,702)	(61,862)
Other income (loss):
Interest (expense) income and other, net	(68)	303
Total other income (loss)	(68)	303
Net loss	(59,770)	(61,559)
Other comprehensive income:
Unrealized gain on short-term securities - available-for-sale	106	78
Total other comprehensive income	106	78
Comprehensive loss	$ (59,664)	$ (61,481)
Net loss per share — basic and diluted	$ (1.31)	$ (1.49)
Weighted average number of shares of common stock outstanding for computing basic and diluted net loss per share	45,697	41,324