Fees and Expenses

Oct. 31, 2025

BNY Mellon Bond Market Index Fund

Prospectus [Line Items]

Expense Heading [Optional Text]

Fees and Expenses

Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and examples below.

Operating Expenses Caption [Optional Text]

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses [Table]

Annual Fund Operating Expenses - BNY Mellon Bond Market Index Fund		Class I Shares	Investor
Management Fees (as a percentage of Assets)		0.15%	0.15%
Distribution and Service (12b-1) Fees		0.00%	0.25%
Other Expenses (as a percentage of Assets):		0.01%	0.01%
Expenses (as a percentage of Assets)		0.16%	0.41%
Fee Waiver or Reimbursement	[1]	(0.01%)	(0.01%)
Net Expenses (as a percentage of Assets)		0.15%	0.40%

Expense Example [Heading]

Example

Expense Example Narrative [Text Block]

The Example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the fund for the time periods indicated and then hold or redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the fund's operating expenses remain the same. The Example is based on net operating expenses, which reflects the contractual undertaking by BNY Mellon Investment Adviser, Inc. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, With Redemption [Table]

Expense Example - BNY Mellon Bond Market Index Fund - USD ($)	Class I Shares	Investor
Expense Example, with Redemption, 1 Year	$ 15	$ 41
Expense Example, with Redemption, 3 Years	48	128
Expense Example, with Redemption, 5 Years	85	224
Expense Example, with Redemption, 10 Years	$ 192	$ 505

Portfolio Turnover [Heading]

Portfolio Turnover

Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 181.20% of the average value of its portfolio.

Portfolio Turnover, Rate

181.20%

BNY Mellon Institutional S&P 500 Stock Index Fund

Prospectus [Line Items]

Expense Heading [Optional Text]

Fees and Expenses

Expense Narrative [Text Block]

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and examples below.

Operating Expenses Caption [Optional Text]

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses [Table]

Annual Fund Operating Expenses - BNY Mellon Institutional S&P 500 Stock Index Fund	Class I
Management Fees (as a percentage of Assets)	0.20%
Other Expenses (as a percentage of Assets):	0.02%
Expenses (as a percentage of Assets)	0.22%
Fee Waiver or Reimbursement	(0.01%)	[1]
Net Expenses (as a percentage of Assets)	0.21%

Expense Example [Heading]

Example

Expense Example Narrative [Text Block]

The Example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the fund for the time periods indicated and then hold or redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the fund's operating expenses remain the same. The Example is based on net operating expenses, which reflects the contractual undertaking by BNY Mellon Investment Adviser, Inc. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, With Redemption [Table]

Expense Example - BNY Mellon Institutional S&P 500 Stock Index Fund	Class I USD ($)
Expense Example, with Redemption, 1 Year	$ 22
Expense Example, with Redemption, 3 Years	68
Expense Example, with Redemption, 5 Years	118
Expense Example, with Redemption, 10 Years	$ 268

Portfolio Turnover [Heading]

Portfolio Turnover

Portfolio Turnover [Text Block]

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 2.69% of the average value of its portfolio.

Portfolio Turnover, Rate

2.69%

[1] The fund's investment adviser, BNY Mellon Investment Adviser, Inc., has agreed in its investment management agreement with the fund to: (1) pay all of the fund's direct expenses, except management fees, Rule 12b-1 fees and certain other expenses, including the fees and expenses of the non-interested board members and their counsel, and (2) reduce its fees pursuant to the investment management agreement in an amount equal to the fund's allocable portion of the fees and expenses of the non-interested board members and their counsel (in the amount of .01% for the past fiscal year). These provisions in the investment management agreement may not be amended without the approval of the fund's shareholders.

[1] The fund's investment adviser, BNY Mellon Investment Adviser, Inc., has agreed in its management agreement with the fund to pay all of the fund's expenses, except management fees, interest expenses, brokerage fees, commissions and commitment fees on borrowings if any, fees pursuant to any distribution or shareholder services plan adopted by the fund, fees and expenses of the non-interested board members and their counsel and independent counsel to the fund, and any extraordinary expenses. BNY Mellon Investment Adviser, Inc. has further agreed to reduce its fees in an amount equal to the fund's allocable portion of the fees and expenses of the non-interested board members and the fees and expenses of counsel to the fund and to the non-interested board members (in the amount of .01% for the past fiscal year). These provisions in the management agreement may not be amended without the approval of the fund's shareholders.