Shareholder Report |
6 Months Ended | |||||||||
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Aug. 31, 2025
USD ($)
shares
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| Shareholder Report [Line Items] | ||||||||||
| Document Type | N-CSRS | |||||||||
| Amendment Flag | false | |||||||||
| Registrant Name | Fidelity California Municipal Trust II | |||||||||
| Entity Central Index Key | 0000878662 | |||||||||
| Entity Investment Company Type | N-1A | |||||||||
| Document Period End Date | Aug. 31, 2025 | |||||||||
| Fidelity California Municipal Money Market Fund | ||||||||||
| Shareholder Report [Line Items] | ||||||||||
| Fund Name | Fidelity® California Municipal Money Market Fund | |||||||||
| Class Name | Fidelity® California Municipal Money Market Fund | |||||||||
| Trading Symbol | FABXX | |||||||||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains information about Fidelity® California Municipal Money Market Fund for the period March 1, 2025 to August 31, 2025. | |||||||||
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |||||||||
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. | |||||||||
| Additional Information Phone Number | 1-800-544-8544 | |||||||||
| Additional Information Email | fidfunddocuments@fidelity.com | |||||||||
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec | |||||||||
| Expenses [Text Block] | What were your Fund costs for the last six months?
(based on hypothetical $10,000 investment)
|
|||||||||
| Expenses Paid, Amount | $ 21 | |||||||||
| Expense Ratio, Percent | 0.42% | |||||||||
| Net Assets | $ 5,631,563,129 | |||||||||
| Holdings Count | shares | 403 | |||||||||
| Additional Fund Statistics [Text Block] | Key Fund Statistics
(as of August 31, 2025)
|
|||||||||
| Holdings [Text Block] | EFFECTIVE MATURITY DIVERSIFICATION (% of Fund's net assets) Days 1-7 67.3 8-30 7.3 31-60 13.2 61-90 4.4 91-180 0.1 >180 5.0 Tender Option Bond 33.5 Variable Rate Demand Notes (VRDNs) 23.3 Commercial Paper 19.4 Municipal Securities 9.4 Net Other Assets (Liabilities) 14.4 ASSET ALLOCATION (% of Fund's net assets) Tender Option Bond - 33.5 Variable Rate Demand Notes (VRDNs) - 23.3 Commercial Paper - 19.4 Municipal Securities - 9.4 Net Other Assets (Liabilities) - 14.4 | |||||||||
| Fidelity California Municipal Money Market Fund - Premium Class | ||||||||||
| Shareholder Report [Line Items] | ||||||||||
| Fund Name | Fidelity® California Municipal Money Market Fund | |||||||||
| Class Name | Fidelity® California Municipal Money Market Fund Premium Class | |||||||||
| Trading Symbol | FSPXX | |||||||||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains information about Fidelity® California Municipal Money Market Fund for the period March 1, 2025 to August 31, 2025. | |||||||||
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |||||||||
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. | |||||||||
| Additional Information Phone Number | 1-800-544-8544 | |||||||||
| Additional Information Email | fidfunddocuments@fidelity.com | |||||||||
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec | |||||||||
| Expenses [Text Block] | What were your Fund costs for the last six months?
(based on hypothetical $10,000 investment)
|
|||||||||
| Expenses Paid, Amount | $ 15 | |||||||||
| Expense Ratio, Percent | 0.30% | |||||||||
| Net Assets | $ 5,631,563,129 | |||||||||
| Holdings Count | shares | 403 | |||||||||
| Additional Fund Statistics [Text Block] | Key Fund Statistics
(as of August 31, 2025)
|
|||||||||
| Holdings [Text Block] | EFFECTIVE MATURITY DIVERSIFICATION (% of Fund's net assets) Days 1-7 67.3 8-30 7.3 31-60 13.2 61-90 4.4 91-180 0.1 >180 5.0 Tender Option Bond 33.5 Variable Rate Demand Notes (VRDNs) 23.3 Commercial Paper 19.4 Municipal Securities 9.4 Net Other Assets (Liabilities) 14.4 ASSET ALLOCATION (% of Fund's net assets) Tender Option Bond - 33.5 Variable Rate Demand Notes (VRDNs) - 23.3 Commercial Paper - 19.4 Municipal Securities - 9.4 Net Other Assets (Liabilities) - 14.4 | |||||||||
| Fidelity California Municipal Money Market Fund - Institutional Class | ||||||||||
| Shareholder Report [Line Items] | ||||||||||
| Fund Name | Fidelity® California Municipal Money Market Fund | |||||||||
| Class Name | Fidelity® California Municipal Money Market Fund Institutional Class | |||||||||
| Trading Symbol | FSBXX | |||||||||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains information about Fidelity® California Municipal Money Market Fund for the period March 1, 2025 to August 31, 2025. | |||||||||
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |||||||||
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-877-208-0098 or by sending an e-mail to fidfunddocuments@fidelity.com. | |||||||||
| Additional Information Phone Number | 1-877-208-0098 | |||||||||
| Additional Information Email | fidfunddocuments@fidelity.com | |||||||||
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec | |||||||||
| Expenses [Text Block] | What were your Fund costs for the last six months?
(based on hypothetical $10,000 investment)
|
|||||||||
| Expenses Paid, Amount | $ 10 | |||||||||
| Expense Ratio, Percent | 0.20% | |||||||||
| Net Assets | $ 5,631,563,129 | |||||||||
| Holdings Count | shares | 403 | |||||||||
| Additional Fund Statistics [Text Block] | Key Fund Statistics
(as of August 31, 2025)
|
|||||||||
| Holdings [Text Block] | EFFECTIVE MATURITY DIVERSIFICATION (% of Fund's net assets) Days 1-7 67.3 8-30 7.3 31-60 13.2 61-90 4.4 91-180 0.1 >180 5.0 Tender Option Bond 33.5 Variable Rate Demand Notes (VRDNs) 23.3 Commercial Paper 19.4 Municipal Securities 9.4 Net Other Assets (Liabilities) 14.4 ASSET ALLOCATION (% of Fund's net assets) Tender Option Bond - 33.5 Variable Rate Demand Notes (VRDNs) - 23.3 Commercial Paper - 19.4 Municipal Securities - 9.4 Net Other Assets (Liabilities) - 14.4 |