Annual report pursuant to Section 13 and 15(d)


Cover - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Mar. 24, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2020    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2020    
Current Fiscal Year End Date --12-31    
Entity File Number 001-38022    
Entity Central Index Key 0001582554    
Entity Tax Identification Number 46-3011414    
Entity Incorporation, State or Country Code DE    
Entity Address, Address Line One 1545 Route 206 South    
Entity Address, Address Line Two Suite 302    
Entity Address, City or Town Bedminster    
Entity Address, State or Province NJ    
Entity Address, Postal Zip Code 07921    
City Area Code 908    
Local Phone Number 443-1860    
Title of 12(b) Security Common Stock, par value $0.0001    
Trading Symbol MTNB    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 141.9
Entity Common Stock, Shares Outstanding   204,276,412