v3.25.2
Shareholder Report
 6 Months Ended
Apr. 30, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name BNY Mellon Index Funds, Inc.
Entity Central Index Key 0000857114
Entity Investment Company Type N-1A
Document Period End Date Apr. 30, 2025
C000000294 [Member]  
Shareholder Report [Line Items]  
Fund Name BNY Mellon International Stock Index Fund
Class Name Investor Shares
Trading Symbol DIISX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BNY Mellon International Stock Index Fund (the “Fund”) for the period of November 1, 2024 to April 30, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at bny.com/investments/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bny.com.
Additional Information Phone Number 1-800-373-9387
Additional Information Email info@bny.com
Additional Information Website bny.com/investments/literaturecenter
Expenses [Text Block]
What were the Fund’s costs for the last six months ?
(based on a hypothetical $10,000 investment)
Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Investor Shares* $31 0.60%**
*
During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
**
Annualized.
Expenses Paid, Amount $ 31 [1]
Expense Ratio, Percent 0.60% [1],[2]
Net Assets $ 315,000,000
Holdings Count | Holding 700
Investment Company Portfolio Turnover 1.74%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 4/30/25 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$315 700 1.74%
Holdings [Text Block]
Portfolio Holdings (as of 4/30/25 )
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
Country Allocation (Based on Net Assets)
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
C000172467 [Member]  
Shareholder Report [Line Items]  
Fund Name BNY Mellon International Stock Index Fund
Class Name Class I
Trading Symbol DINIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BNY Mellon International Stock Index Fund (the “Fund”) for the period of November 1, 2024 to April 30, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at bny.com/investments/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bny.com.
Additional Information Phone Number 1-800-373-9387
Additional Information Email info@bny.com
Additional Information Website bny.com/investments/literaturecenter
Expenses [Text Block]
What were the Fund’s costs for the last six months ?
(based on a hypothetical $10,000 investment)
Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Class I* $18 0.35%**
*
During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
**
Annualized.
Expenses Paid, Amount $ 18 [3]
Expense Ratio, Percent 0.35% [3],[4]
Net Assets $ 315,000,000
Holdings Count | Holding 700
Investment Company Portfolio Turnover 1.74%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 4/30/25 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$315 700 1.74%
Holdings [Text Block]
Portfolio Holdings (as of 4/30/25 )
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
Country Allocation (Based on Net Assets)
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
C000000295 [Member]  
Shareholder Report [Line Items]  
Fund Name BNY Mellon S&P 500 Index Fund
Class Name BNY Mellon S&P 500 Index Fund
Trading Symbol PEOPX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BNY Mellon S&P 500 Index Fund (the “Fund”) for the period of November 1, 2024 to April 30, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at bny.com/investments/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bny.com.
Additional Information Phone Number 1-800-373-9387
Additional Information Email info@bny.com
Additional Information Website bny.com/investments/literaturecenter
Expenses [Text Block]
What were the Fund’s costs for the last six months ?
(based on a hypothetical $10,000 investment)
Fund Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
BNY Mellon S&P 500 Index Fund* $25 0.50%**
*
During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
**
Annualized.
Expenses Paid, Amount $ 25 [5]
Expense Ratio, Percent 0.50% [5],[6]
Net Assets $ 2,221,000,000
Holdings Count | Holding 506
Investment Company Portfolio Turnover 1.10%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 4/30/25 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$2,221 506 1.10%
Holdings [Text Block]
Portfolio Holdings (as of 4/30/25 )
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
Sector Allocation (Based on Net Assets)
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
C000000296 [Member]  
Shareholder Report [Line Items]  
Fund Name BNY Mellon Smallcap Stock Index Fund
Class Name Investor Shares
Trading Symbol DISSX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BNY Mellon Smallcap Stock Index Fund (the “Fund”) for the period of November 1, 2024 to April 30, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at bny.com/investments/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bny.com.
Additional Information Phone Number 1-800-373-9387
Additional Information Email info@bny.com
Additional Information Website bny.com/investments/literaturecenter
Expenses [Text Block]
What were the Fund’s costs for the last six months ?
(based on a hypothetical $10,000 investment)
Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Investor Shares* $23 0.50%**
*
During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
**
Annualized.
Expenses Paid, Amount $ 23 [7]
Expense Ratio, Percent 0.50% [7],[8]
Net Assets $ 819,000,000
Holdings Count | Holding 607
Investment Company Portfolio Turnover 26.64%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 4/30/25 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$819 607 26.64%
Holdings [Text Block]
Portfolio Holdings (as of 4/30/25 )
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
Sector Allocation (Based on Net Assets)
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
C000172468 [Member]  
Shareholder Report [Line Items]  
Fund Name BNY Mellon Smallcap Stock Index Fund
Class Name Class I
Trading Symbol DISIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about BNY Mellon Smallcap Stock Index Fund (the “Fund”) for the period of November 1, 2024 to April 30, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at bny.com/investments/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bny.com.
Additional Information Phone Number 1-800-373-9387
Additional Information Email info@bny.com
Additional Information Website bny.com/investments/literaturecenter
Expenses [Text Block]
What were the Fund’s costs for the last six months ?
(based on a hypothetical $10,000 investment)
Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Class I* $12 0.25%**
*
During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
**
Annualized.
Expenses Paid, Amount $ 12 [9]
Expense Ratio, Percent 0.25% [9],[10]
Net Assets $ 819,000,000
Holdings Count | Holding 607
Investment Company Portfolio Turnover 26.64%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 4/30/25 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$819 607 26.64%
Holdings [Text Block]
Portfolio Holdings (as of 4/30/25 )
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
Sector Allocation (Based on Net Assets)
Graphical Representation - Allocation 1 Chart
Largest Holdings [Text Block]
Top Ten Holdings (Based on Net Assets) *
Graphical Representation - Top N Holdings Chart
* Excludes money market funds or other short-term securities held for the investment of cash and cash collateral for securities loaned, if any.
[1] During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
[2] Annualized.
[3] During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
[4] Annualized.
[5] During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
[6] Annualized.
[7] During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
[8] Annualized.
[9] During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc.
[10] Annualized.