| Form N-CSR Cover | 6 Months Ended |
| Nov. 30, 2024 | |
| 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 |
| 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 | |
| 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 $ 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 ) $ 193 8.43 % | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) Sector Allocation (Based on Net Assets) | |
| 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 | |
| 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 $ 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 ) $ 193 8.43 % | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) 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 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 | |
| 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 $ 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 ) $ 193 8.43 % | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) 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 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 | |
| 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 $ 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 ) $ 193 8.43 % | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) 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 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 | |
| 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 $ 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 ) $ 193 8.43 % | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) Sector Allocation (Based on Net Assets) | |
| [1]Annualized.[2]Annualized.[3]Annualized.[4]Annualized.[5]Annualized. | ||
| Shareholder Report, Holdings (Details) | Nov. 30, 2024 |
| C000001378 [Member] | Transportation Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| C000001378 [Member] | Medical [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| C000001378 [Member] | Airport [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.60% |
| C000001378 [Member] | Education [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| C000001378 [Member] | Nursing Homes [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000001378 [Member] | Multifamily Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000001378 [Member] | Tobacco Settlement [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000001378 [Member] | Power [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| C000001378 [Member] | School District [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000001378 [Member] | Development [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| C000001378 [Member] | Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| C000001378 [Member] | General Obligation [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| C000001378 [Member] | Net Other Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.40% |
| C000001376 [Member] | Transportation Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| C000001376 [Member] | Medical [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| C000001376 [Member] | Airport [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.60% |
| C000001376 [Member] | Education [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| C000001376 [Member] | Nursing Homes [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000001376 [Member] | Multifamily Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000001376 [Member] | Tobacco Settlement [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000001376 [Member] | Power [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| C000001376 [Member] | School District [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000001376 [Member] | Development [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| C000001376 [Member] | Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| C000001376 [Member] | General Obligation [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| C000001376 [Member] | Net Other Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.40% |
| C000073387 [Member] | Transportation Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| C000073387 [Member] | Medical [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| C000073387 [Member] | Airport [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.60% |
| C000073387 [Member] | Education [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| C000073387 [Member] | Nursing Homes [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000073387 [Member] | Multifamily Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000073387 [Member] | Tobacco Settlement [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000073387 [Member] | Power [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| C000073387 [Member] | School District [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000073387 [Member] | Development [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| C000073387 [Member] | Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| C000073387 [Member] | General Obligation [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| C000073387 [Member] | Net Other Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.40% |
| C000130450 [Member] | Transportation Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| C000130450 [Member] | Medical [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| C000130450 [Member] | Airport [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.60% |
| C000130450 [Member] | Education [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| C000130450 [Member] | Nursing Homes [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000130450 [Member] | Multifamily Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000130450 [Member] | Tobacco Settlement [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000130450 [Member] | Power [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| C000130450 [Member] | School District [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000130450 [Member] | Development [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| C000130450 [Member] | Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| C000130450 [Member] | General Obligation [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| C000130450 [Member] | Net Other Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.40% |
| C000000023 [Member] | Transportation Sector [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| C000000023 [Member] | Medical [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| C000000023 [Member] | Airport [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.60% |
| C000000023 [Member] | Education [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| C000000023 [Member] | Nursing Homes [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000000023 [Member] | Multifamily Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| C000000023 [Member] | Tobacco Settlement [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000000023 [Member] | Power [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| C000000023 [Member] | School District [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000000023 [Member] | Development [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| C000000023 [Member] | Housing [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| C000000023 [Member] | General Obligation [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| C000000023 [Member] | Net Other Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.40% |
