This annual shareholder report contains important information about BNY Mellon California AMT-Free Municipal Bond Fund, Inc. (the “Fund”) for the period of June 1, 2024 to May 31, 2025.

Shareholder Report Annual or Semi-Annual

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 year ?

(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 A	$86	0.86%

Expenses Paid, Amount

$ 86

Expense Ratio, Percent

0.86%

Factors Affecting Performance [Text Block]

How did the Fund perform last year ?

For the 12-month period ended May 31, 2025, the Fund’s Class A shares returned 0.86%.
In comparison, the Bloomberg U.S. Municipal Bond Index (the “Index”) returned 2.03% for the same period.

What affected the Fund’s performance?

The municipal bond market was generally flat during the reporting period. A significant primary supply of bonds proved to be a headwind for the market.
The Fund’s performance relative to the Index benefited from overweight exposure to BBB-rated securities.
Relative performance suffered due to overweight exposure to California securities and revenue bonds issued by hospitals and colleges, all of which underperformed the market.

Not FDIC Insured. Not Bank-Guaranteed. May Lose Value

Performance Past Does Not Indicate Future [Text]

The Fund’s past performance is not a good predictor of the Fund’s future performance.

Line Graph [Table Text Block]

How did the Fund perform over the past 10 years?

The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.

Cumulative Performance from June 1 , 2015 through May 31, 2025
Initial Investment of $10,000

The above graph compares a hypothetical $10,000 investment in the Fund’s Class A shares to a hypothetical investment of $10,000 made in the Bloomberg U.S. Municipal Bond Index on 5/31/2015. The performance shown takes into account the maximum initial sales charge on Class A shares and applicable fees and expenses of the Fund, including management fees and other expenses. The Fund’s performance also assumes the reinvestment of dividends and capital gains. Unlike the Fund, the Index is not subject to charges, fees and other expenses. Investors cannot invest directly in any index.

Average Annual Return [Table Text Block]

AVERAGE ANNUAL TOTAL RETURNS (AS OF 5/31/25 )

Class A Shares	1YR	5YR	10YR
with Maximum Sales Charge - 4.50%	-3.69%	-0.89%	0.95%
without Sales Charge	0.86%	0.03%	1.42%
Bloomberg U.S. Municipal Bond Index	2.03%	0.55%	2.13%

No Deduction of Taxes [Text Block]

The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.

Updated Performance Information Location [Text Block]

For more current information visit bny.com/investments/literaturecenter .

Net Assets

$ 527,000,000

Holdings Count | Holding

184

Advisory Fees Paid, Amount

$ 2,557,557

Investment Company Portfolio Turnover

12.39%

Additional Fund Statistics [Text Block]

KEY FUND STATISTICS (AS OF 5/31/25 )

Fund Size (Millions)	Number of Holdings	Total Advisory Fee Paid During Period	Annual Portfolio Turnover
$527	184	$2,557,557	12.39%

Holdings [Text Block]

Portfolio Holdings (as of 5/31/25 )

Sector Allocation (Based on Net Assets)

Graphical Representation - Top N Holdings Chart

C000001376 [Member]

Shareholder Report [Line Items]

Fund Name

BNY Mellon California AMT-Free Municipal Bond Fund, Inc.

Class Name

Class C

Trading Symbol

DCACX

Annual or Semi-Annual Statement [Text Block]

This annual shareholder report contains important information about BNY Mellon California AMT-Free Municipal Bond Fund, Inc. (the “Fund”) for the period of June 1, 2024 to May 31, 2025.

Shareholder Report Annual or Semi-Annual

annual shareholder report

Additional Information [Text Block]

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 year ?

(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 C	$164	1.64%

Expenses Paid, Amount

$ 164

Expense Ratio, Percent

1.64%

Factors Affecting Performance [Text Block]

How did the Fund perform last year ?

For the 12-month period ended May 31, 2025, the Fund’s Class C shares returned 0.08%.
In comparison, the Bloomberg U.S. Municipal Bond Index (the “Index”) returned 2.03% for the same period.

What affected the Fund’s performance?

The municipal bond market was generally flat during the reporting period. A significant primary supply of bonds proved to be a headwind for the market.
The Fund’s performance relative to the Index benefited from overweight exposure to BBB-rated securities.
Relative performance suffered due to overweight exposure to California securities and revenue bonds issued by hospitals and colleges, all of which underperformed the market.

Not FDIC Insured. Not Bank-Guaranteed. May Lose Value

Performance Past Does Not Indicate Future [Text]

The Fund’s past performance is not a good predictor of the Fund’s future performance.

Line Graph [Table Text Block]

How did the Fund perform over the past 10 years?

Cumulative Performance from June 1 , 2015 through May 31, 2025
Initial Investment of $10,000

The above graph compares a hypothetical $10,000 investment in the Fund’s Class C shares to a hypothetical investment of $10,000 made in the Bloomberg U.S. Municipal Bond Index on 5/31/2015. The performance shown takes into account the maximum deferred sales charge on Class C shares and applicable fees and expenses of the Fund, including management fees, 12b-1 fees and other expenses. The Fund’s performance also assumes the reinvestment of dividends and capital gains. Unlike the Fund, the Index is not subject to charges, fees and other expenses. Investors cannot invest directly in any index.

Average Annual Return [Table Text Block]

AVERAGE ANNUAL TOTAL RETURNS (AS OF 5/31/25 )

Class C Shares	1YR		5YR	10YR
with Maximum Deferred Sales Charge - 1.00%	-0.91%	*	-0.73%	0.65%
without Deferred Sales Charge	0.08%		-0.73%	0.65%
Bloomberg U.S. Municipal Bond Index	2.03%		0.55%	2.13%

*	The maximum contingent deferred sales charge for Class C shares is 1.00% for shares redeemed within one year of the date purchased.

No Deduction of Taxes [Text Block]

The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.

Updated Performance Information Location [Text Block]

For more current information visit bny.com/investments/literaturecenter .

Net Assets

$ 527,000,000

Holdings Count | Holding

184

Advisory Fees Paid, Amount

$ 2,557,557

Investment Company Portfolio Turnover

12.39%

Additional Fund Statistics [Text Block]

KEY FUND STATISTICS (AS OF 5/31/25 )

Fund Size (Millions)	Number of Holdings	Total Advisory Fee Paid During Period	Annual Portfolio Turnover
$527	184	$2,557,557	12.39%

Holdings [Text Block]

Portfolio Holdings (as of 5/31/25 )

Sector Allocation (Based on Net Assets)

C000073387 [Member]

Shareholder Report [Line Items]

Fund Name

BNY Mellon California AMT-Free Municipal Bond Fund, Inc.

Class Name

Class I

Trading Symbol

DCMIX

Annual or Semi-Annual Statement [Text Block]

This annual shareholder report contains important information about BNY Mellon California AMT-Free Municipal Bond Fund, Inc. (the “Fund”) for the period of June 1, 2024 to May 31, 2025.

Shareholder Report Annual or Semi-Annual

annual shareholder report

Additional Information [Text Block]

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 year ?

(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	$62	0.62%

Expenses Paid, Amount

$ 62

Expense Ratio, Percent

0.62%

Factors Affecting Performance [Text Block]

How did the Fund perform last year ?

For the 12-month period ended May 31, 2025, the Fund’s Class I shares returned 1.10%.
In comparison, the Bloomberg U.S. Municipal Bond Index (the “Index”) returned 2.03% for the same period.

What affected the Fund’s performance?

The municipal bond market was generally flat during the reporting period. A significant primary supply of bonds proved to be a headwind for the market.
The Fund’s performance relative to the Index benefited from overweight exposure to BBB-rated securities.
Relative performance suffered due to overweight exposure to California securities and revenue bonds issued by hospitals and colleges, all of which underperformed the market.

Not FDIC Insured. Not Bank-Guaranteed. May Lose Value

Performance Past Does Not Indicate Future [Text]

The Fund’s past performance is not a good predictor of the Fund’s future performance.

Line Graph [Table Text Block]

How did the Fund perform over the past 10 years?

Cumulative Performance from June 1 , 2015 through May 31, 2025
Initial Investment of $10,000

The above graph compares a hypothetical $10,000 investment in the Fund’s Class I shares to a hypothetical investment of $10,000 made in the Bloomberg U.S. Municipal Bond Index on 5/31/2015. The performance shown takes into account applicable fees and expenses of the Fund, including management fees and other expenses. The Fund’s performance also assumes the reinvestment of dividends and capital gains. Unlike the Fund, the Index is not subject to charges, fees and other expenses. Investors cannot invest directly in any index.

Average Annual Return [Table Text Block]

AVERAGE ANNUAL TOTAL RETURNS (AS OF 5/31/25 )

Share Class	1YR	5YR	10YR
Class I	1.10%	0.27%	1.67%
Bloomberg U.S. Municipal Bond Index	2.03%	0.55%	2.13%

No Deduction of Taxes [Text Block]

The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.

Updated Performance Information Location [Text Block]

For more current information visit bny.com/investments/literaturecenter .

Net Assets

$ 527,000,000

Holdings Count | Holding

184

Advisory Fees Paid, Amount

$ 2,557,557

Investment Company Portfolio Turnover

12.39%

Additional Fund Statistics [Text Block]

KEY FUND STATISTICS (AS OF 5/31/25 )

Fund Size (Millions)	Number of Holdings	Total Advisory Fee Paid During Period	Annual Portfolio Turnover
$527	184	$2,557,557	12.39%

Holdings [Text Block]

Portfolio Holdings (as of 5/31/25 )

Sector Allocation (Based on Net Assets)

C000130450 [Member]

Shareholder Report [Line Items]

Fund Name

BNY Mellon California AMT-Free Municipal Bond Fund, Inc.

Class Name

Class Y

Trading Symbol

DCAYX

Annual or Semi-Annual Statement [Text Block]

This annual shareholder report contains important information about BNY Mellon California AMT-Free Municipal Bond Fund, Inc. (the “Fund”) for the period of June 1, 2024 to May 31, 2025.

Shareholder Report Annual or Semi-Annual

annual shareholder report

Additional Information [Text Block]

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 year ?

(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 Y	$58	0.58%

Expenses Paid, Amount

$ 58

Expense Ratio, Percent

0.58%

Factors Affecting Performance [Text Block]

How did the Fund perform last year ?

For the 12-month period ended May 31, 2025, the Fund’s Class Y shares returned 1.17%.
In comparison, the Bloomberg U.S. Municipal Bond Index (the “Index”) returned 2.03% for the same period.

What affected the Fund’s performance?

The municipal bond market was generally flat during the reporting period. A significant primary supply of bonds proved to be a headwind for the market.
The Fund’s performance relative to the Index benefited from overweight exposure to BBB-rated securities.
Relative performance suffered due to overweight exposure to California securities and revenue bonds issued by hospitals and colleges, all of which underperformed the market.

Not FDIC Insured. Not Bank-Guaranteed. May Lose Value

Performance Past Does Not Indicate Future [Text]

The Fund’s past performance is not a good predictor of the Fund’s future performance.

Line Graph [Table Text Block]

How did the Fund perform over the past 10 years?

Cumulative Performance from June 1 , 2015 through May 31, 2025
Initial Investment of $1,000,000

The above graph compares a hypothetical $1,000,000 investment in the Fund’s Class Y shares to a hypothetical investment of $1,000,000 made in the Bloomberg U.S. Municipal Bond Index on 5/31/2015. The performance shown takes into account applicable fees and expenses of the Fund, including management fees and other expenses. The Fund’s performance also assumes the reinvestment of dividends and capital gains. Unlike the Fund, the Index is not subject to charges, fees and other expenses. Investors cannot invest directly in any index.

Average Annual Return [Table Text Block]

AVERAGE ANNUAL TOTAL RETURNS (AS OF 5/31/25 )

Share Class	1YR	5YR	10YR
Class Y	1.17%	0.21%	1.65%
Bloomberg U.S. Municipal Bond Index	2.03%	0.55%	2.13%

No Deduction of Taxes [Text Block]

The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares.

Updated Performance Information Location [Text Block]

For more current information visit bny.com/investments/literaturecenter .

Net Assets

$ 527,000,000

Holdings Count | Holding

184

Advisory Fees Paid, Amount

$ 2,557,557

Investment Company Portfolio Turnover

12.39%

Additional Fund Statistics [Text Block]

KEY FUND STATISTICS (AS OF 5/31/25 )

Fund Size (Millions)	Number of Holdings	Total Advisory Fee Paid During Period	Annual Portfolio Turnover
$527	184	$2,557,557	12.39%

Holdings [Text Block]

Portfolio Holdings (as of 5/31/25 )

Sector Allocation (Based on Net Assets)

C000000023 [Member]

Shareholder Report [Line Items]

Fund Name

BNY Mellon California AMT-Free Municipal Bond Fund, Inc.

Class Name

Class Z

Trading Symbol

DRCAX

Annual or Semi-Annual Statement [Text Block]

This annual shareholder report contains important information about BNY Mellon California AMT-Free Municipal Bond Fund, Inc. (the “Fund”) for the period of June 1, 2024 to May 31, 2025.

Shareholder Report Annual or Semi-Annual

annual shareholder report

Additional Information [Text Block]

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 year ?

(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 Z	$67	0.67%

Expenses Paid, Amount

$ 67

Expense Ratio, Percent

0.67%

Factors Affecting Performance [Text Block]

How did the Fund perform last year ?

For the 12-month period ended May 31, 2025, the Fund’s Class Z shares returned 1.07%.
In comparison, the Bloomberg U.S. Municipal Bond Index (the “Index”) returned 2.03% for the same period.

What affected the Fund’s performance?

The municipal bond market was generally flat during the reporting period. A significant primary supply of bonds proved to be a headwind for the market.
The Fund’s performance relative to the Index benefited from overweight exposure to BBB-rated securities.
Relative performance suffered due to overweight exposure to California securities and revenue bonds issued by hospitals and colleges, all of which underperformed the market.

Not FDIC Insured. Not Bank-Guaranteed. May Lose Value

Performance Past Does Not Indicate Future [Text]

The Fund’s past performance is not a good predictor of the Fund’s future performance.

Line Graph [Table Text Block]

How did the Fund perform over the past 10 years?

Cumulative Performance from June 1 , 2015 through May 31, 2025
Initial Investment of $10,000

The above graph compares a hypothetical $10,000 investment in the Fund’s Class Z shares to a hypothetical investment of $10,000 made in the Bloomberg U.S. Municipal Bond Index on 5/31/2015. The performance shown takes into account applicable fees and expenses of the Fund, including management fees and other expenses. The Fund’s performance also assumes the reinvestment of dividends and capital gains. Unlike the Fund, the Index is not subject to charges, fees and other expenses. Investors cannot invest directly in any index.

Average Annual Return [Table Text Block]

AVERAGE ANNUAL TOTAL RETURNS (AS OF 5/31/25 )