v3.26.1
S000020012 [Member] N-1A Cover
Dec. 31, 2025
Prospectus [Line Items]  
Document Type 485BPOS
Amendment Flag false
Registrant Name NUVEEN INVESTMENT FUNDS INC
Entity Central Index Key 0000820892
Entity Investment Company Type N-1A
Document Period End Date Dec. 31, 2025
Prospectus Date Apr. 30, 2026