v3.26.1
Form N-CSR Cover
6 Months Ended
Jun. 30, 2026
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name BNY Mellon Stock Index Fund, Inc.
Entity Central Index Key 0000846800
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026