Cover Page - shares	3 Months Ended
	Mar. 31, 2025	Jun. 30, 2025
Document Information [Line Items]
Document Type	10-Q
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2025
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001872228
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 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	No
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
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