v3.26.1
Document and Entity Information
Mar. 30, 2026
Document Information [Line Items]  
Document Type 8-K
Document Period End Date Mar. 30, 2026
Entity Registrant Name TERRESTRIAL ENERGY INC.
Entity Incorporation, State or Country Code DE
Entity File Number 001-42252
Entity Tax Identification Number 98-1785406
Entity Address, Address Line One 2730 W. Tyvola Road
Entity Address, Adress Line Two Suite 100
Entity Address, City or Town Charlotte
Entity Address State Or Province NC
Entity Address, Postal Zip Code 28217
City Area Code 646
Local Phone Number 687-8212
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Entity Emerging Growth Company true
Entity Ex Transition Period false
Entity Central Index Key 0002019804
Amendment Flag false
Common Stock, par value $0.0001 per share  
Document Information [Line Items]  
Title of 12(b) Security Common Stock, par value $0.0001 per share
Trading Symbol IMSR
Security Exchange Name NASDAQ
Redeemable Warrants, each whole warrant exercisable for one Common Stock at a price of $11.50 per share  
Document Information [Line Items]  
Title of 12(b) Security Redeemable Warrants, each whole warrant exercisable for one CommonStock at a price of $11.50 per share
Trading Symbol IMSRW
Security Exchange Name NASDAQ