v3.26.1
N-2 - $ / shares
1 Months Ended 12 Months Ended
Mar. 31, 2024
Mar. 31, 2025
Cover [Abstract]    
Entity Central Index Key   0001976685
Amendment Flag   false
Entity Inv Company Type   N-2
Document Type   N-CSR
Entity Registrant Name   Institutional Investment Strategy Fund
Founder Class    
General Description of Registrant [Abstract]    
NAV Per Share $ 10.82  
Capital Stock, Long-Term Debt, and Other Securities [Abstract]    
Outstanding Security, Held [Shares] 726,186  
Investor Class    
General Description of Registrant [Abstract]    
NAV Per Share $ 10.8  
Capital Stock, Long-Term Debt, and Other Securities [Abstract]    
Outstanding Security, Held [Shares] 1,065