Shareholder Report |
6 Months Ended | |||||||||
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Aug. 31, 2026
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, 2026 | |||||||||
| 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, 2026 to August 31, 2026. | |||||||||
| 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 | $ 6,917,673,857 | |||||||||
| Holdings Count | shares | 436 | |||||||||
| Additional Fund Statistics [Text Block] | Key Fund Statistics
(as of August 31, 2026)
|
|||||||||
| Holdings [Text Block] | EFFECTIVE MATURITY DIVERSIFICATION (% of Fund's net assets) Days 1-7 43.1 8-30 35.9 31-60 9.4 61-90 3.2 91-180 4.9 >180 4.0 Tender Option Bond 36.6 Variable Rate Demand Notes (VRDNs) 23.9 Commercial Paper 18.1 Municipal Securities 8.1 Net Other Assets (Liabilities) 13.3 ASSET ALLOCATION (% of Fund's net assets) Tender Option Bond - 36.6 Variable Rate Demand Notes (VRDNs) - 23.9 Commercial Paper - 18.1 Municipal Securities - 8.1 Net Other Assets (Liabilities) - 13.3 | |||||||||
| 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, 2026 to August 31, 2026. | |||||||||
| 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 | $ 6,917,673,857 | |||||||||
| Holdings Count | shares | 436 | |||||||||
| Additional Fund Statistics [Text Block] | Key Fund Statistics
(as of August 31, 2026)
|
|||||||||
| Holdings [Text Block] | EFFECTIVE MATURITY DIVERSIFICATION (% of Fund's net assets) Days 1-7 43.1 8-30 35.9 31-60 9.4 61-90 3.2 91-180 4.9 >180 4.0 Tender Option Bond 36.6 Variable Rate Demand Notes (VRDNs) 23.9 Commercial Paper 18.1 Municipal Securities 8.1 Net Other Assets (Liabilities) 13.3 ASSET ALLOCATION (% of Fund's net assets) Tender Option Bond - 36.6 Variable Rate Demand Notes (VRDNs) - 23.9 Commercial Paper - 18.1 Municipal Securities - 8.1 Net Other Assets (Liabilities) - 13.3 | |||||||||
| 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, 2026 to August 31, 2026. | |||||||||
| 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 | $ 6,917,673,857 | |||||||||
| Holdings Count | shares | 436 | |||||||||
| Additional Fund Statistics [Text Block] | Key Fund Statistics
(as of August 31, 2026)
|
|||||||||
| Holdings [Text Block] | EFFECTIVE MATURITY DIVERSIFICATION (% of Fund's net assets) Days 1-7 43.1 8-30 35.9 31-60 9.4 61-90 3.2 91-180 4.9 >180 4.0 Tender Option Bond 36.6 Variable Rate Demand Notes (VRDNs) 23.9 Commercial Paper 18.1 Municipal Securities 8.1 Net Other Assets (Liabilities) 13.3 ASSET ALLOCATION (% of Fund's net assets) Tender Option Bond - 36.6 Variable Rate Demand Notes (VRDNs) - 23.9 Commercial Paper - 18.1 Municipal Securities - 8.1 Net Other Assets (Liabilities) - 13.3 |