Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended		6 Months Ended
	Oct. 31, 2012	Jun. 30, 2012	Jun. 30, 2015
Commitments And Contingencies [Line Items]
Percentage of requisite preferred holders who approved plan to set aside proceeds of any sale of to be distributed	60.00%
Lease expiration term			The Company leases office and laboratory space under two non-cancelable operating leases in Tucson, Arizona, which were set to expire in November and December 2015, respectively, as of June 30, 2015. Under the terms of the two Tucson leases, the Company had one option to extend the leases for five years at the end of the initial seven year lease term.
Lease extension term, in years			5 years
Expected increase in lease rent			$ 804,000
Additional commitment expense			$ 500,000
Merck Sharp And Dohme Corporation [Member]
Commitments And Contingencies [Line Items]
Non-exclusive license agreement, milestone accrued or paid		$ 0
Tucson
Commitments And Contingencies [Line Items]
Lease extension term, in years			5 years
Lease term			7 years
Minimum
Commitments And Contingencies [Line Items]
Percentage of proceeds of any sale to be distributed to employees, directors, or consultants	15.00%
Minimum | Merck Sharp And Dohme Corporation [Member]
Commitments And Contingencies [Line Items]
Non-exclusive license agreement, contingent milestone payments		$ 50,000
Non-exclusive license agreement, future royalties		3.00%
Maximum | Merck Sharp And Dohme Corporation [Member]
Commitments And Contingencies [Line Items]
Non-exclusive license agreement, contingent milestone payments		$ 1,000,000
Non-exclusive license agreement, future royalties		6.00%