Risk/Return Detail Data - FidelitySustainableMulti-AssetFund-AMCIPRO	Nov. 29, 2022 USD ($)
Risk/Return:
Registrant Name	Fidelity Charles Street Trust
FidelitySustainableMulti-AssetFund-AMCIPRO | Fidelity Sustainable Multi-Asset Fund
Risk/Return:
Risk/Return [Heading]	Fund Summary Fund /Class: Fidelity® Sustainable Multi-Asset Fund /Fidelity Advisor® Sustainable Multi-Asset Fund A, M, C, I
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	Fidelity® Sustainable Multi-Asset Fund seeks total return.
Expense [Heading]	Fee Table
Expense Narrative [Text Block]	The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund. In addition to the fees and expenses described below, your broker may also require you to pay brokerage commissions on purchases and sales of certain share classes of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 34 of the prospectus. Different intermediaries may provide additional waivers or reductions of the sales charge. Please see "Sales Charge Waiver Policies Applied by Certain Intermediaries" in the "Appendix" section of the prospectus.
Shareholder Fees Caption [Text]	Shareholder fees
Operating Expenses Caption [Text]	Annual Operating Expenses
Fee Waiver or Reimbursement over Assets, Date of Termination	Jan. 31, 2024
Portfolio Turnover [Heading]	Portfolio Turnover
Portfolio Turnover [Text Block]	The fund will not incur transaction costs, such as commissions, when it buys and sells shares of underlying Fidelity ® funds (or "turns over" its portfolio), but it could incur transaction costs if it were to buy and sell other types of securities directly. If the fund were to buy and sell other types of securities directly, a higher portfolio turnover rate could indicate higher transaction costs and could result in higher taxes when fund shares are held in a taxable account. Such costs, if incurred, would not be reflected in annual operating expenses or in the example and would affect the fund's performance. For the period from February 10, 2022 to September 30, 2022, the fund's portfolio turnover rate was 111 % (annualized) of the average value of its portfolio.
Portfolio Turnover, Rate	111.00%
Expenses Deferred Charges [Text Block]	Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.
Expense Breakpoint Discounts [Text]	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 34 of the prospectus.
Expense Breakpoint, Minimum Investment Required [Amount]	$ 50,000
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.
Expense Example Narrative [Text Block]	This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated and if you hold your shares:
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	Normally investing at least 80% of assets in Fidelity® funds (including mutual funds and Exchange Traded Funds (ETFs)) that invest in securities of issuers that Fidelity Management & Research Company LLC (FMR) (the Adviser) believes have proven or improving sustainability practices based on an evaluation of such issuer's individual environmental, social, and governance (ESG) profile and in Fidelity® index funds that track an ESG index (underlying Fidelity funds). Allocating assets according to a neutral asset allocation strategy in which 70% of the fund's assets are allocated to underlying Fidelity® U.S. and international equity mutual funds and ETFs and 30% to underlying Fidelity® bond mutual funds and ETFs. To reflect the Adviser's market outlook, which is primarily focused on the intermediate term, the Adviser may overweight or underweight each asset class within the following ranges: equity funds (60%-80%) and bond funds (20%-40%). The Adviser may invest up to 10% of the fund's total assets in commodities, high yield debt (also referred to as junk bonds), floating rate debt, real estate debt, international debt, emerging markets debt or short term funds, but no more than 25% in aggregate within those asset classes. Emerging markets include countries that have an emerging stock market as defined by MSCI, countries or markets with low- to middle-income economies as classified by the World Bank, and other countries or markets that the Adviser identifies as having similar emerging markets characteristics. Buying and selling futures contracts (both long and short positions) in an effort to manage cash flows efficiently, remain fully invested, or facilitate asset allocation. Actively managed underlying funds employ sustainable investing exclusion criteria to avoid investments in issuers that are directly engage in, and/or derive significant revenue from, certain industries. Please see "Fund Basics - Investment Details - Sustainable Investing Exclusions" for additional information.
Risk [Heading]	Principal Investment Risks
Risk Narrative [Text Block]	Asset Allocation Risk. The fund is subject to risks resulting from the Adviser's asset allocation decisions. The selection of underlying funds and the allocation of the fund's assets among various asset classes could cause the fund to lose value or its results to lag relevant benchmarks or other funds with similar objectives. Investing in Other Funds. The fund bears all risks of investment strategies employed by the underlying funds, including the risk that the underlying funds will not meet their investment objectives. Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments. Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease. Sustainability Risk. Application of FMR's ESG ratings process and/or its sustainable investing exclusion criteria may affect the fund's exposure to certain issuers, sectors, regions, and countries and may affect the fund's performance depending on whether certain investments are in or out of favor. The criteria related to the fund's ESG ratings process and/or adherence to its sustainable investing exclusion criteria may result in the fund forgoing opportunities to buy certain securities when it might otherwise be advantageous to do so, or selling securities for ESG reasons when it might be otherwise disadvantageous for it to do so. As a result, the fund's performance may at times be better or worse than the performance of funds that do not use ESG or sustainability criteria. There are significant differences in interpretations of what it means for an issuer to have positive ESG factors. While the Adviser believes its definitions are reasonable, the portfolio decisions it makes may differ with other investors' or advisers' views. When evaluating an issuer, the Adviser is dependent on information or data obtained through voluntary or third-party reporting that may be incomplete, inaccurate, or unavailable, which could cause the Adviser to incorrectly assess an issuer's business practices. Foreign and Emerging Markets Risk. Foreign markets, particularly emerging markets, can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. The extent of economic development; political stability; market depth, infrastructure, and capitalization; and regulatory oversight can be less than in more developed markets. Emerging markets typically have less established legal, accounting and financial reporting systems than those in more developed markets, which may reduce the scope or quality of financial information available to investors. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile. Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change. Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. Changes in the financial condition of an issuer or counterparty (e.g., broker-dealer or other borrower in a securities lending transaction) can increase the risk of default by an issuer or counterparty, which can affect a security's or instrument's value or result in delays in recovering securities and/or capital from a counterparty. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease. Correlation to Index. The performance of an underlying index fund and its index may vary somewhat due to factors such as fees and expenses of the underlying fund, transaction costs, sample selection, regulatory restrictions, and timing differences associated with additions to and deletions from the index. Errors in the construction or calculation of the index may occur from time to time and may not be identified and corrected for some period of time, which may have an adverse impact on an underlying fund and its shareholders. Passive Management Risk. Some of the underlying funds in which the fund invests are managed with a passive investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of an underlying fund's index or of the actual securities included in the index. This differs from an actively managed fund, which typically seeks to outperform a benchmark index. As a result, the performance of these underlying funds could be lower than actively managed funds that may shift their portfolio assets to take advantage of market opportunities or lessen the impact of a market decline or a decline in the value of one or more issuers. An underlying index fund may be concentrated to approximately the same extent that its index concentrates in the securities of issuers in a particular industry or group of industries. Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly. Investing in ETFs. ETFs may trade in the secondary market at prices below the value of their underlying portfolios and may not be liquid. ETFs that track an index are subject to tracking error and may be unable to sell poorly performing assets that are included in their index or other benchmark. High Portfolio Turnover. High portfolio turnover (more than 100%) may result in increased transaction costs and potentially higher capital gains or losses. The effects of higher than normal portfolio turnover may adversely affect the fund's performance. An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency .   You could lose money by investing in the fund.
Risk Lose Money [Text]	You could lose money by investing in the fund.
Risk Not Insured Depository Institution [Text]	An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency .
Bar Chart and Performance Table [Heading]	Performance
Performance Narrative [Text Block]	Performance history will be available for the fund after the fund has been in operation for one calendar year.
Performance One Year or Less [Text]	Performance history will be available for the fund after the fund has been in operation for one calendar year.
FidelitySustainableMulti-AssetFund-AMCIPRO | Fidelity Sustainable Multi-Asset Fund | Fidelity Advisor Sustainable Multi-Asset Fund - Class I
Risk/Return:
Maximum sales charge (load) on purchases (as a % of offering price)	none
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	none
Management fee	0.10%
Distribution and/or Service (12b-1) fees	none
Other expenses	none
Acquired fund fees and expenses	0.51%
Total annual operating expenses	0.61%
Fee waiver and/or expense reimbursement	0.05%
Total annual operating expenses after fee waiver and/or expense reimbursement	0.56%
1 year	$ 57
3 years	189
5 years	334
10 years	756
1 Year	57
3 Years	189
5 Years	334
10 Years	$ 756
FidelitySustainableMulti-AssetFund-AMCIPRO | Fidelity Sustainable Multi-Asset Fund | Fidelity Advisor Sustainable Multi-Asset Fund - Class M
Risk/Return:
Maximum sales charge (load) on purchases (as a % of offering price)	3.50%
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	none	[1]
Management fee	0.10%
Distribution and/or Service (12b-1) fees	0.50%
Other expenses	none
Acquired fund fees and expenses	0.51%
Total annual operating expenses	1.11%
Fee waiver and/or expense reimbursement	0.05%
Total annual operating expenses after fee waiver and/or expense reimbursement	1.06%
1 year	$ 454
3 years	684
5 years	934
10 years	1,649
1 Year	454
3 Years	684
5 Years	934
10 Years	$ 1,649
FidelitySustainableMulti-AssetFund-AMCIPRO | Fidelity Sustainable Multi-Asset Fund | Fidelity Advisor Sustainable Multi-Asset Fund - Class C
Risk/Return:
Maximum sales charge (load) on purchases (as a % of offering price)	none
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	1.00%	[2]
Management fee	0.10%
Distribution and/or Service (12b-1) fees	1.00%
Other expenses	none
Acquired fund fees and expenses	0.51%
Total annual operating expenses	1.61%
Fee waiver and/or expense reimbursement	0.05%
Total annual operating expenses after fee waiver and/or expense reimbursement	1.56%
Expenses Deferred Charges [Text Block]	On Class C shares redeemed less than one year after purchase.
1 year	$ 259
3 years	501
5 years	870
10 years	1,704
1 Year	159
3 Years	501
5 Years	870
10 Years	$ 1,704
FidelitySustainableMulti-AssetFund-AMCIPRO | Fidelity Sustainable Multi-Asset Fund | Fidelity Advisor Sustainable Multi-Asset Fund - Class A
Risk/Return:
Maximum sales charge (load) on purchases (as a % of offering price)	5.75%
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	none	[1]
Management fee	0.10%
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	none
Acquired fund fees and expenses	0.51%
Total annual operating expenses	0.86%
Fee waiver and/or expense reimbursement	0.05%
Total annual operating expenses after fee waiver and/or expense reimbursement	0.81%
1 year	$ 653
3 years	827
5 years	1,018
10 years	1,569
1 Year	653
3 Years	827
5 Years	1,018
10 Years	$ 1,569

[1] A Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

[2] B On Class C shares redeemed less than one year after purchase.