Subsequent Event (Details) (USD $)	3 Months Ended		6 Months Ended		91 Months Ended		2 Months Ended	10 Months Ended	0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 ContraVir Contribution Agreement	Jun. 30, 2013 ContraVir Contribution Agreement	Jun. 05, 2013 ContraVir Promissory note	Aug. 08, 2013 Subsequent event ContraVir	Jul. 08, 2013 Subsequent event ContraVir Shared Services Agreement Minimum
Subsequent Event
Number of shares issued of common stock							9,000,000
Common stock, par value (in dollars per share)	$ 0.0001		$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Percentage of outstanding shares of common stock upon issuance							100.00%
Research and development expenditures	$ 9,055,000	$ 7,626,000	$ 23,399,000	$ 12,964,000	$ 81,106,000			$ 0
Net book value of asset contributed							0	0
Maximum amount that the subsidiary agreed to repay entity in relation to a promissory note									500,000
Unpaid principal amount of advances made to subsidiaries									$ 100,000
Interest rate (as a percent)									6.00%
Period of prior written notice for demanding payment of unpaid principal amount and all accrued but unpaid interest thereon at anytime after specified date									15 days
Period of prior written notice for termination of agreement											30 days
Period of failure to perform material obligations after receipt of written notice for termination of agreement											30 days
Percentage of common stock for a potential distribution to the entity's stockholders										100.00%