Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended		151 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013
Quarterly Financial Information [Line Items]
Net loss arising during development stage	$ (3,215)	$ (2,753)	$ (2,754)	$ (2,464)	$ (2,101)	$ (2,269)	$ (1,541)	$ (1,612)	$ (11,186)	$ (7,523)	$ (96,297)
Basic and diluted loss per share	$ (0.19)	$ (0.18)	$ (0.50)	$ (0.70)	$ (0.71)	$ (0.93)	$ (0.78)	$ (1.01)	$ (1.10)	$ (3.35)