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Shareholder Report
 6 Months Ended
Nov. 30, 2024
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name BNY Mellon California AMT-Free Municipal Bond Fund, Inc.
Entity Central Index Key 0000720064
Entity Investment Company Type N-1A
Document Period End Date Nov. 30, 2024
C000001378 [Member]  
Shareholder Report [Line Items]  
Fund Name BNY Mellon California AMT-Free Municipal Bond Fund, Inc.
Class Name Class A
Trading Symbol DCAAX
Annual or Semi-Annual Statement [Text Block] This semi-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 November 30, 2024.
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 A $45 0.88%*
*
Annualized.
Expenses Paid, Amount $ 45
Expense Ratio, Percent 0.88% [1]
Net Assets $ 580,000,000
Holdings Count | Holding 193
Investment Company Portfolio Turnover 8.43%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 11/30/24 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$580 193 8.43%
Holdings [Text Block]
Portfolio Holdings (as of 11/30/24 )
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 semi-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 November 30, 2024.
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 C $85 1.66%*
*
Annualized.
Expenses Paid, Amount $ 85
Expense Ratio, Percent 1.66% [2]
Net Assets $ 580,000,000
Holdings Count | Holding 193
Investment Company Portfolio Turnover 8.43%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 11/30/24 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$580 193 8.43%
Holdings [Text Block]
Portfolio Holdings (as of 11/30/24 )
Sector Allocation (Based on Net Assets)
Graphical Representation - Top N Holdings Chart
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 semi-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 November 30, 2024.
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 $33 0.64%*
*
Annualized.
Expenses Paid, Amount $ 33
Expense Ratio, Percent 0.64% [3]
Net Assets $ 580,000,000
Holdings Count | Holding 193
Investment Company Portfolio Turnover 8.43%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 11/30/24 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$580 193 8.43%
Holdings [Text Block]
Portfolio Holdings (as of 11/30/24 )
Sector Allocation (Based on Net Assets)
Graphical Representation - Top N Holdings Chart
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 semi-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 November 30, 2024.
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 Y $31 0.60%*
*
Annualized.
Expenses Paid, Amount $ 31
Expense Ratio, Percent 0.60% [4]
Net Assets $ 580,000,000
Holdings Count | Holding 193
Investment Company Portfolio Turnover 8.43%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 11/30/24 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$580 193 8.43%
Holdings [Text Block]
Portfolio Holdings (as of 11/30/24 )
Sector Allocation (Based on Net Assets)
Graphical Representation - Top N Holdings Chart
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 semi-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 November 30, 2024.
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 Z $35 0.69%*
*
Annualized.
Expenses Paid, Amount $ 35
Expense Ratio, Percent 0.69% [5]
Net Assets $ 580,000,000
Holdings Count | Holding 193
Investment Company Portfolio Turnover 8.43%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (AS OF 11/30/24 )

Fund Size (Millions)
Number of Holdings
Portfolio Turnover
$580 193 8.43%
Holdings [Text Block]
Portfolio Holdings (as of 11/30/24 )
Sector Allocation (Based on Net Assets)
Graphical Representation - Top N Holdings Chart
[1] Annualized.
[2] Annualized.
[3] Annualized.
[4] Annualized.
[5] Annualized.