v3.26.1
First Trust Emerging Markets Small Cap AlphaDEX Fund N-1A Cover
Dec. 31, 2025
Prospectus [Line Items]  
Document Type 485BPOS
Amendment Flag false
Registrant Name First Trust Exchange-Traded AlphaDEX ® Fund II
Entity Central Index Key 0001510337
Entity Investment Company Type N-1A
Document Period End Date Dec. 31, 2025
Prospectus Date May 01, 2026