v3.25.4
S000042178 [Member] N-1A Cover
Sep. 30, 2025
Prospectus [Line Items]  
Document Type 485BPOS
Amendment Flag false
Registrant Name BARON INVESTMENT FUNDS TRUST (f/k/a BARON ASSET FUND)
Entity Central Index Key 0000810902
Entity Investment Company Type N-1A
Document Period End Date Sep. 30, 2025
Prospectus Date Jan. 28, 2026