Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY PHILLIPS STREET TRUST
Prospectus Date	rr_ProspectusDate	Jan. 29, 2015
Retail \| Fidelity Cash Reserves
Risk/Return:	rr_RiskReturnAbstract
Supplement [Text Block]	fpst_SupplementTextBlock	Supplement to the Fidelity^® Cash Reserves and Fidelity U.S. Government Reserves January 29, 2015 Prospectus The Board of Trustees has approved, subject to shareholder approval, a proposal to modify Fidelity Cash Reserves' fundamental concentration policy so that the fund would be prohibited from investing more than 25% of its total assets in the financial services industry. A meeting of shareholders of Fidelity Cash Reserves will be held on May 12, 2015, to vote on this proposal. If approved by shareholders, the fund will make other changes necessary to operate as a government money market fund, including (ii) adopting a principal investment strategy to normally invest at least 99.5% of its total assets in cash, government securities, and/or repurchase agreements that are collateralized fully and (ii) changing its name to "Fidelity Government Cash Reserves." If approved, the fund currently anticipates that these changes will take effect in the fourth quarter of 2015. Effective May 31, 2015, Fidelity U.S. Government Reserves' principal investment strategies as set forth in the "Fund Summary" and "Fund Basics" sections of the prospectus are revised so that the Adviser normally invests at least 99.5% of the fund's total assets in cash, U.S. Government securities and/or repurchase agreements that are collateralized fully. This policy is subject to change only upon 60 days' prior notice to shareholders.

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY PHILLIPS STREET TRUST

Prospectus Date

rr_ProspectusDate

Jan. 29, 2015

Retail | Fidelity Cash Reserves

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

fpst_SupplementTextBlock

Supplement to the
Fidelity^® Cash Reserves and Fidelity U.S. Government Reserves
January 29, 2015
Prospectus

The Board of Trustees has approved, subject to shareholder approval, a proposal to modify Fidelity Cash Reserves' fundamental concentration policy so that the fund would be prohibited from investing more than 25% of its total assets in the financial services industry. A meeting of shareholders of Fidelity Cash Reserves will be held on May 12, 2015, to vote on this proposal. If approved by shareholders, the fund will make other changes necessary to operate as a government money market fund, including (ii) adopting a principal investment strategy to normally invest at least 99.5% of its total assets in cash, government securities, and/or repurchase agreements that are collateralized fully and (ii) changing its name to "Fidelity Government Cash Reserves." If approved, the fund currently anticipates that these changes will take effect in the fourth quarter of 2015.

Effective May 31, 2015, Fidelity U.S. Government Reserves' principal investment strategies as set forth in the "Fund Summary" and "Fund Basics" sections of the prospectus are revised so that the Adviser normally invests at least 99.5% of the fund's total assets in cash, U.S. Government securities and/or repurchase agreements that are collateralized fully. This policy is subject to change only upon 60 days' prior notice to shareholders.