v3.26.1
Cover Page - USD ($)
 12 Months Ended
Dec. 31, 2025
Mar. 30, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2025    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Central Index Key 0001872228    
Document Transition Report false    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Entity File Number 001-42641    
Entity Registrant Name THAYER VENTURES ACQUISITION CORPORATION II    
Entity Incorporation, State or Country Code E9    
Entity Address, Address Line One 25852 McBean Parkway Suite 508    
Entity Address, City or Town Valencia    
Entity Tax Identification Number 98-1795713    
Entity Address, State or Province CA    
Entity Address, Postal Zip Code 91355    
City Area Code 415    
Local Phone Number 782-1414    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period false    
Entity Shell Company true    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Public Float     $ 139,169,586.7
ICFR Auditor Attestation Flag false    
Auditor Name WithumSmith+Brown, PC    
Auditor Firm ID 100    
Auditor Location New York    
Document Financial Statement Error Correction [Flag] false    
Units, each consisting of one Class A Ordinary Share, par value $0.0001 per share, and one Right entitling the holder to receive one-tenth of a Class A Ordinary Share [Member]      
Document Information [Line Items]      
Title of 12(b) Security Units, each consisting of one Class A Ordinary Share, par value $0.0001 per share,    
Trading Symbol TVAIU    
Security Exchange Name NASDAQ    
Class A ordinary share [Member]      
Document Information [Line Items]      
Title of 12(b) Security Class A Ordinary Shares, par value $0.0001 per share    
Trading Symbol TVAI    
Security Exchange Name NASDAQ    
Entity Common Stock, Shares Outstanding   20,487,500  
Class B ordinary share [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   6,708,333  
Rights [Member]      
Document Information [Line Items]      
Title of 12(b) Security Rights    
Trading Symbol TVAIR    
Security Exchange Name NASDAQ