Document And Entity Information - shares
6 Months Ended
Jun. 30, 2019
Jul. 25, 2019
Document And Entity Information [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Jun. 30, 2019  
Entity File Number 001-36860  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 75-3254381  
Entity Address, Address Line One 999 Skyway Road, Suite 150  
Entity Address, City or Town San Carlos  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94070  
City Area Code 650  
Local Phone Number 260-7120  
Title of 12(b) Security Common stock, par value $0.000041666 per value  
Trading Symbol IOVA  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   123,830,506
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Entity Central Index Key 0001425205  
Amendment Flag false