v3.25.4
FT Vest 20+ Year Treasury & Target Income ETF N-1A Cover
Oct. 31, 2025
Prospectus [Line Items]  
Document Type 485BPOS
Amendment Flag false
Registrant Name First Trust Exchange-Traded Fund IV
Entity Central Index Key 0001517936
Entity Investment Company Type N-1A
Document Period End Date Oct. 31, 2025
Prospectus Date Mar. 02, 2026