Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Details)

Commitments and Contingencies (Details) (Corporate headquarters and research and development laboratory, USD $)
0 Months Ended
Dec. 31, 2014
Dec. 31, 2014
Operating Lease    
Number of rentable square feet 33,928us-gaap_AreaOfRealEstateProperty 33,928us-gaap_AreaOfRealEstateProperty
Term of Lease Agreement 120 months  
Period by which the lease term can be extended 5 years  
Monthly base rent under Lease Agreement (per rentable square feet) 2.65oncs_BaseRentPerRentableSquareFeetUnderLeaseAgreement  
Annual base rent increase (as a percent) 3.00%oncs_AnnualBaseRentIncreaseInPercentage  
Period for Rent Commencement Date 12 months  
Initial deposit $ 90,000us-gaap_SecurityDeposit $ 90,000us-gaap_SecurityDeposit
Operating Lease    
Notice period prior to expiration of the term for extending the Lease Agreement 12 months  
Operating Lease    
Notice period for terminating the lease agreement 12 months