Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended			84 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2012
Consolidated Statements of Comprehensive Loss [Abstract]
Revenues:	$ 0	$ 0	$ 0	$ 0
Operating expenses:
General and administrative	14,723	6,178	3,720	31,576
Research and development	21,443	14,788	9,334	60,681
Total operating expenses	36,166	20,966	13,054	92,257
Loss from operations	(36,166)	(20,966)	(13,054)	(92,257)
Interest income	340	45	26	713
Interest expense	(3)	(2)	(5)	(119)
Foreign currency transaction gain	145	29	0	174
Realized gain on short-term investments	215	0	0	214
Unrealized gain (loss) on short-term investments	(2)	0	0	(2)
Adjustment to fair value of common stock warrants	(3,173)	(16,301)	(5,895)	(25,369)
Net loss	(38,644)	(37,195)	(18,928)	(116,646)
Other comprehensive income (loss)
Foreign currency translation adjustment	(52)	10	(8)	(50)
Comprehensive loss	$ (38,696)	$ (37,185)	$ (18,936)	$ (116,696)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.80)	$ (1.15)	$ (0.85)
Weighted average shares outstanding used to compute:
Basic and diluted (in shares)	48,085	32,327	22,227