Objective, Primary [Text Block]

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Risk/Return [Heading]

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GREEN CENTURY BALANCED FUND SUMMARY SECTION

Objective [Heading]

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Investment Objective

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The Green Century Balanced Fund seeks capital growth and income from a diversified portfolio of stocks and bonds which meet Green Century’s standards for corporate environmental responsibility.

Expense [Heading]

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Fees and Expenses of the Fund

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. If you invest in shares of the Fund through an investment professional or financial intermediary, that investment professional or financial intermediary may charge you a commission in an amount determined and separately disclosed to you by that investment professional or financial intermediary.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 9% of the average value of its portfolio.

Portfolio Turnover, Rate

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9.00%

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This example is intended to help you compare the costs of investing in the Fund with the cost of investing in other mutual funds. This example assumes that: (1) you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods; (2) your investment has a 5%

return each year; and (3) the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund invests primarily in the stocks and bonds of U.S. companies the Fund’s Adviser, Green Century Capital Management (Green Century), believes are environmentally responsible and sustainable. Green Century defines its standard for environmentally responsible and sustainable as seeking to provide an opportunity to invest in a way that avoids environmentally dangerous industries which impose onerous costs on society and the planet. There is no predetermined percentage of assets allocated to either stocks or bonds, although the Fund will generally invest at least 25% of its net assets in bonds and may not invest more than 75% of its net assets in stocks.

The Fund seeks to promote environmentally responsible corporate behavior, a cleaner environment and a sustainable economy by investing its assets in companies that Green Century believes are environmentally responsible and sustainable. Green Century applies rigorous selection criteria to identify such companies, which may include, but are not limited to, those that:

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Demonstrate a commitment to preserving and enhancing the environment as evidenced by the products they make and the services they provide;

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Make positive contributions toward actively promoting a healthier environmental future, including companies that produce renewable energy products, help conserve water, promote sustainable agriculture, and those that offer effective remedies for existing environmental problems;

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Strive to openly disclose their policies and performance on critical environmental criteria;

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Respond positively to shareholder advocacy on environmental, social and governance (ESG) issues.

The Fund also seeks to work with the companies in which it invests to adopt stronger environmental policies for their operations and supply chains.

Green Century believes that companies that seek to manage their environmental risks may enjoy competitive advantages from cost reductions, quality improvements, profitability enhancements and access to expanding and new growth markets. Further, Green Century believes that companies that are responsible towards the environment are more likely to act ethically and maintain the trust of their shareholders.

Green Century believes that environmentally dangerous industries impose onerous costs on society and the planet and seeks to provide an opportunity to invest in a way that avoids them; thus at various times the Fund may not be invested in certain companies and industries Green Century believes threaten a sustainable global environment and public health. The Balanced Fund does not intend to invest in companies that primarily:

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Explore for, extract, produce, manufacture or refine coal, oil or gas or produce or transmit electricity derived from fossil fuels or transmit natural gas or have material carbon reserves;

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Are engaged in the production of nuclear energy or the manufacture of nuclear equipment to produce nuclear energy or nuclear weapons, in the belief that these products are unacceptably threatening to a sustainable global environment;

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Are engaged in the manufacture of tobacco products, which are linked to air pollution, deforestation, and plastic pollution, as well as health problems;

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Serve as factory farms, which pollute our drinking water and overuse medically important antibiotics;

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Are involved in genetically modified organisms (GMOs) whose use has led to increased use of toxic herbicides;

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Produce firearms or military weapons; or

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Are engaged in gambling and alcohol.

The Fund may invest in growth and value stocks of any market capitalization. The Fund may be more heavily weighted in growth stocks. The Fund’s Subadviser uses quantitative measurements in combination with in-house and third-party research to analyze the stocks of companies identified using Green Century’s environmental criteria, and the Subadviser’s own proprietary ESG integrated investment process, and includes in the Fund’s portfolio those companies that appear to possess superior earnings growth prospects and whose stock prices, in the Subadviser’s opinion, do not accurately reflect the companies’ value. The Subadviser’s in-house research consists of an internally generated analysis using its proprietary investment process. Third-party information providers for both financial and ESG data currently include Bloomberg, L.P., MSCI Inc. and FactSet. The Subadviser may sell a stock in the Fund’s portfolio, if, among other reasons, the company no longer meets the Fund’s environmental standards or the stock no longer meets the Fund’s investment criteria or becomes overvalued relative to the long-term expectation for its stock price.

As a baseline eligibility process, the Subadviser performs an ESG-integrated fundamental research process which includes both industry benchmarking and in-depth company analyses that covers both quantitative and qualitative considerations. In terms of industry reviews, the Subadviser conducts an industry benchmarking evaluation using ESG data weighted according to specific factors deemed by the Subadviser to have the most financial impact for the industry. In terms of the company review, the Subadviser conducts an in depth ESG analysis that evaluates the scope and integrity of a company’s products, policies, and practices related to ESG issues. The ESG criteria reviewed by the Subadviser reflect a variety of key sustainability issues that can influence company risks and opportunities. The ESG criteria implemented by the Subadviser may differ between industries.

The bonds the Fund invests in may be of any maturity. While the Fund’s fixed income investments will be primarily invested in investment grade bonds, the Fund may invest up to 35% of its net assets in high yield, below investment grade bonds, commonly known as “junk bonds.” The Fund’s fixed income investments

consist primarily of corporate bonds, U.S. Government securities, securities issued by supra-national or foreign domiciled entities, municipal securities, and mortgage-related securities, and may include bonds also determined to be “green” by the Subadviser based on the use of proceeds supporting climate change mitigation and adaptation, among other environmental goals.

In general, fixed income securities are included in the Fund’s portfolio to balance or offset risks associated with the Fund’s investment in stocks. Fixed income investments are evaluated using the Fund’s environmental criteria. Issuer-specific financial evaluation of fixed income investments focuses on an issuer’s cash flow, interest rate coverage, and other measures of its ability to meet its future income and principal repayment commitments. In addition, each fixed income investment is evaluated with respect to its credit quality and its overall exposure to interest rate risk.

The Fund may invest up to 30% of its assets in equity and debt securities of non-U.S. issuers.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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You may lose money by investing in the Fund. As with any mutual fund, there can be no guarantee that the Fund will achieve its objective. The following is a summary description of certain risks of investing in the Fund:

Market Risk. The market prices of securities, or other assets held by the Fund may fall, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic or political conditions, recessions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets, the spread of infectious illness or other public health issues, armed conflict, market disruptions caused by tariffs, trade disputes, sanctions or other government actions, or other factors or adverse investor sentiment. If the market prices of the Fund’s securities and assets fall, the value of your investment will go down. A change in financial condition or other event affecting a single issuer or market may adversely impact securities markets as a whole. Rates of inflation have recently risen. The value of assets or income from an investment may be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the Fund’s assets can decline as can the value of the Fund’s distributions.

Changes in market conditions will not typically have the same impact on all types of securities. The market prices of securities may fall due to factors affecting a particular issuer, industry or the securities market as a whole. In the past decade, financial markets throughout the world have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. Governmental and non‑ governmental issuers have defaulted on, or been forced to restructure, their debts. These conditions may continue, recur, worsen or spread. Events that have contributed to these market conditions include, but are not limited to major cybersecurity events; geopolitical events (including wars, terror attacks and economic sanctions); measures to address budget deficits; downgrading of sovereign debt; changes in oil and commodity prices; dramatic changes in currency exchange rates; global pandemics; and public sentiment. The global pandemic of the novel coronavirus respiratory disease designated COVID‑19 has resulted in major disruption to economies and markets around the world, including the United States. Global financial markets have experienced extreme volatility and severe losses, and trading in many instruments has been disrupted. Liquidity for many instruments has been greatly reduced for periods of time. Some sectors of the economy and individual issuers have experienced particularly large losses. These circumstances may

continue for an extended period of time, and may continue to affect adversely the value and liquidity of the Fund’s investments. Following Russia’s invasion of Ukraine, Russian securities have lost all, or nearly all, their market value. Other securities or markets could be similarly affected by past or future geopolitical or other events or conditions.

Governments and central banks, including the U.S. Federal Reserve, have taken extraordinary and unprecedented actions to support local and global economies and the financial markets. These actions have resulted in significant expansion of public debt, including in the U.S. The consequences of high public debt, including its future impact on the economy and securities markets, may not be known for some time. Although they have started to increase, interest rates are still very low, which means there is more risk that they may go up. U.S. Federal Reserve or other U.S. or non‑U.S. governmental or central bank actions, including increases or decreases in interest rates, or contrary actions by different governments could negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the Fund invests. Policy and legislative changes in the United States and in other countries are affecting many aspects of financial regulation and these and other events affecting global markets, such as the United Kingdom’s exit from the European Union (or Brexit), potential trade imbalances with China or other countries, or sanctions or other government actions against Russia, other nations or individuals or companies (or their countermeasures), may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the implications for market participants, may not be fully known for some time.

Economies and financial markets throughout the world are increasingly interconnected. Economic, financial or political events, trading and tariff arrangements, armed conflict including Russia’s military invasion of Ukraine, terrorism, natural disasters, infectious illness or other public health issues, cybersecurity events, supply chain disruptions, sanctions against Russia, other nations or individuals or companies and possible countermeasures, and other circumstances in one country or region could have profound impacts on other countries or regions and on global economies or markets. As a result, whether or not the Fund invests in securities of issuers located in or with significant exposure to the countries or regions directly affected, the value and liquidity of the Fund’s investments may be negatively affected.

Environmentally Responsible Investing Risk. The Fund’s environmental criteria limit the available investments compared with funds with no such criteria. Under certain economic conditions, this could cause the Fund’s investment performance to be worse or better than similar funds with no such criteria. The Subadviser may use third party ESG ratings information that it believes to be reliable, but such information may not be accurate or complete, or may be biased.

Portfolio Selection Risk. The Subadviser’s judgment about a particular security or issuer, or about the economy or a particular sector, region, market segment or industry, or about an investment strategy, may prove to be incorrect or may not produce the desired results, or there may be imperfections, errors or limitations in the models, tools and information used by the Subadviser.

Equity Securities Risk. The Fund is heavily invested in stocks. Like all funds invested in stocks, the Fund’s share price will fluctuate daily depending on the performance of the companies that comprise the Fund’s investments, the general market and the economy overall. After you invest, the value of your shares may be less than what you paid for them.

Small- and Mid‑Cap Companies Risk. The Fund may be invested in small- and mid‑cap companies which involve greater risk than investing in the stocks of larger, more established companies. Small- and mid‑cap companies may lack the management experience, financial resources and product diversification of large companies and the frequency and volume of their trading may be less than that of larger companies. Therefore, securities of small- and mid‑cap companies may be subject to wider and more erratic price fluctuations. Compared to large‑cap companies, small‑cap and mid‑cap companies, and the market for their equity securities, may be more sensitive to changes in earnings results and investor expectations or poor economic or market conditions, including those experienced during a recession, experience sharper swings in market values, have limited liquidity, be harder to value or to sell at the times and prices the Subadviser thinks appropriate, and offer greater potential for gain and loss.

Interest Rate Risk. The market prices of the Fund’s fixed income securities may fluctuate significantly when interest rates change. When interest rates rise, the value of fixed income securities, and therefore the value of your investment in the Fund, generally goes down. A rise in rates tends to have a greater impact on the prices of longer term or duration securities. In recent years interest rates and credit spreads in the U.S. have been at historic lows, which means there is more risk that they may go up. The U.S. Federal Reserve has recently started to raise certain interest rates. A general rise in interest rates could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the Fund. During periods of rising interest rates, the average life of certain types of fixed income securities may be extended because of slower than expected principal payments. This may lock in a below market interest rate, increase the security’s duration (a measure of the underlying portfolio’s price sensitivity to changes in prevailing interest rates) and reduce the value of the security. The maturity of a security may be significantly longer than its effective duration. A security’s maturity and other features may be more relevant than its effective duration in determining the security’s sensitivity to other factors affecting the issuer or markets generally, such as changes in credit quality or in the yield premium that the market may establish for certain types of securities (sometimes called “credit spread”). In general, the longer its maturity the more a security may be susceptible to these factors. When the credit spread for a fixed income security goes up or “widens,” the value of the security will generally go down. When interest rates decline, investments made by the Fund may pay a lower interest rate, which would reduce income received and distributed by the Fund. Also, when interest rates go down, the Fund’s yield will decline. During periods of declining interest rates, the issuer of a fixed income security (or borrowers in a pool of loans) may prepay principal earlier than scheduled, forcing the Fund to reinvest in lower yielding securities. The Fund also may lose any premium it paid on the security.

Credit Risk. If an issuer or guarantor of a fixed income security held by the Fund or a counterparty to a financial contract with the Fund defaults on its obligation to pay principal and/or interest, has its credit rating downgraded or is perceived to be less creditworthy, becomes insolvent or files for bankruptcy, or the credit quality or value of any underlying assets declines, the value of your investment will decline. Changes in actual or perceived creditworthiness may occur quickly. The fund could be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty.

LIBOR Risk. The Fund’s investments, payment obligations and financing terms may be based on floating rates, such as LIBOR (London Interbank Offered Rate) or Secured Overnight Financing Rate (SOFR). ICE Benchmark Administration, the administrator of LIBOR, ceased publication of most LIBOR settings on a

representative basis at the end of 2021 and is expected to cease publication of a majority of U.S. dollar LIBOR settings on a representative basis after June 30, 2023. In addition, global regulators have announced that, with limited exceptions, no new LIBOR-based contracts should be entered into after 2021. The transition away from LIBOR may lead to increased volatility and illiquidity in markets that currently rely on LIBOR and may adversely affect the fund’s performance. The transition may also result in a reduction in the value of certain LIBOR-based investments held by the fund or reduce the effectiveness of related transactions such as hedges.

High Yield or “Junk” Bond Risk. Debt securities that are below investment grade, “junk bonds,” are speculative, have a higher risk of default or are already in default, tend to be less liquid and are more difficult to value than higher grade securities. Junk bonds tend to be volatile and more susceptible to adverse events and negative sentiments.

U.S. Government Agency Obligations Risk. Government sponsored entities such as Federal National Mortgage Association (Fannie Mae), Federal Home Loan Mortgage Corporation (Freddie Mac) and the Federal Home Loan Banks (FHLBs), although chartered or sponsored by Congress, are not funded by congressional appropriations and the debt and mortgage-backed securities issued by them are neither guaranteed nor issued by the U.S. government. Although the U.S. government has provided financial support to Fannie Mae and Freddie Mac in the past, there can be no assurance that it will support these or other government sponsored entities in the future.

Municipal Securities Risk. The municipal bond market can be susceptible to unusual volatility, particularly for lower-rated and unrated securities. Liquidity can be reduced unpredictably in response to overall economic conditions or credit tightening. Municipal issuers may be adversely affected by rising health care costs, increasing unfunded pension liabilities, and by the phasing out of federal programs providing financial support. Unfavorable conditions and developments relating to projects financed with municipal securities can result in lower revenues to issuers of municipal securities, potentially resulting in defaults. Issuers often depend on revenues from those projects to make principal and interest payments. The value of municipal securities can also be adversely affected by changes in the financial condition of one or more individual municipal issuers or insurers of municipal issuers, regulatory and political developments, tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. Municipal issuers may be more susceptible to downgrades or defaults during recessions or similar periods of economic stress. Financial difficulties of municipal issuers may continue or worsen, particularly in the event of economic or market turmoil or a recessions.

Mortgage-Related Securities Risk. The value of mortgage-related securities will be influenced by factors affecting the assets underlying such securities. As a result, during periods of declining asset value, difficult or frozen credit markets, swings in interest rates, or deteriorating economic conditions, mortgage-related securities may decline in value, face valuation difficulties, become more volatile and/or become illiquid. These securities are also subject to prepayment and call risk. Some of these securities may receive little or no collateral protection from the underlying assets and are thus subject to the risk of default. The risk of such defaults is generally higher in the case of mortgage-backed investments issued by non‑governmental issuers and those that include so‑called “sub‑prime” mortgages. The structure of some of these securities may be complex and there may be less available information than for other types of debt securities. Upon the

occurrence of certain triggering events or defaults, the Fund may become the holder of underlying assets at a time when those assets may be difficult to sell or may be sold only at a loss.

Risks of Non‑U.S. Investments. Investing in non‑U.S. issuers or in securities of U.S. issuers with significant exposure to foreign markets may involve unique risks compared to investing in securities of U.S. issuers. These risks are more pronounced for issuers in emerging markets or to the extent that the Fund invests significantly in one region or country. These risks may include different financial reporting practices and regulatory standards, less liquid trading markets, currency risks, changes in economic, political, regulatory and social conditions, armed conflict including Russia’s military invasion of Ukraine, and sanctions or other government actions against Russia, other nations or individuals or companies (or their countermeasures), sustained economic downturns, reduction of government or central bank support, inadequate accounting standards, tariffs, tax dispute or other tax burdens, natural disasters, terrorism, nationalization or expropriation of assets, arbitrary application of laws and regulations or lack of rule of law, and investment and repatriation restrictions. Emerging market economies tend to be less diversified than those of more developed countries. They typically have fewer medical and economic resources than more developed countries and thus they may be less able to control or mitigate the effects of a pandemic.

Market Sector Risk. The Fund may hold a large percentage of securities in a single market sector. To the extent the Fund holds a large percentage of securities in a single sector, its performance will be tied closely to and affected by the performance of that sector, and the Fund will be subject to a greater degree to any market price movements, regulatory or technological change, economic conditions or other developments or risks affecting such market sector than a fund without the same focus.

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Financial Sector Risk. Issuers in the financial sector, such as banks, insurance companies and broker- dealers, may be sensitive to changes in interest rates, credit rating downgrades, decreased liquidity in credit markets, and general economic activity and are generally subject to extensive government regulation.

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Technology Sector Risk. Securities in the technology sector, such as information technology, communications equipment, computer hardware and software, and office and scientific equipment, are generally subject to risks of rapidly evolving technology, short product lives, rates of corporate expenditures, falling prices and profits, competition from new market entrants, and general economic conditions. They are also heavily dependent on intellectual property rights and may be adversely affected by the loss or impairment of, or inability to enforce, those rights.

Liquidity Risk. Liquidity risk exists when particular investments are difficult to purchase or sell. When the Fund holds these types of investments, the Fund’s portfolio may be more difficult to value, especially during periods of market turmoil or due to adverse changes in the conditions of a particular issuer. Markets may become illiquid when there are few, if any, interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities or when dealer market-making capacity is otherwise reduced. During times of market turmoil, there have been, and may be, no buyers for securities in entire asset classes, including U.S. Treasury securities. As a general matter, dealers recently have been less willing to make markets for fixed income securities. When the Fund holds illiquid investments, the Fund may be harder to value, especially in changing markets. Investments by the Fund in derivatives, below investment grade securities, foreign securities, and corporate loans tend to involve greater liquidity risk. If the Fund is forced to sell or unwind these investments to meet redemptions or for other cash needs or try to limit losses, the

Fund may suffer a substantial loss or may not be able to sell at all. Additionally, the market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and the difficulty in purchasing and selling such securities, may be unable to achieve its desired level of exposure to certain sectors. Further, certain securities, once sold, may not settle for an extended period. The Fund will not receive its sales proceeds until that time, which may constrain the Fund’s ability to meet its obligations (including obligations to redeeming shareholders). Liquidity risk may be magnified in an environment of rising interest rates or widening credit spreads in which investor redemptions from fixed income funds may be higher than normal.

Valuation Risk. A significant percentage of the Fund’s securities are valued using a fair value methodology. The sales price the Fund could receive for any particular portfolio investment may differ from the Fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets. These differences may increase significantly and affect Fund investments more broadly during periods of market volatility. Investors who purchase or redeem Fund shares may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the Fund had not fair-valued securities or had used a different valuation methodology. The Fund’s ability to value its investments may be impacted by technological issues and/or errors by pricing services or other third party service providers.

Redemption Risk. The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. Redemption risk is greater to the extent that the Fund has investors with large shareholdings, short investment horizons, or unpredictable cash flow needs. In addition, redemption risk is heightened during periods of overall market turmoil. The redemption by one or more large shareholders of their holdings in the Fund could hurt performance and/or cause the remaining shareholders in the Fund to lose money. Further, if one decision maker has control of Fund shares owned by separate Fund shareholders, including clients or affiliates of the Fund’s Adviser, redemptions by these shareholders may further increase the Fund’s redemption risk. If the Fund is forced to liquidate its assets under unfavorable conditions or at inopportune times, the value of your investment could decline.

Cybersecurity Risk. Cybersecurity failures by or breaches of the Fund’s Adviser, Subadviser, transfer agent, distributor, custodian, fund accounting agent or other service providers may disrupt Fund operations, interfere with the Fund’s ability to calculate its NAV, prevent Fund shareholders from purchasing, redeeming or exchanging shares or receiving distributions or receiving timely information regarding the Fund or their investment in the Fund, cause loss of or unauthorized access to private shareholder information, and result in financial losses to the Fund and its shareholders, regulatory fines, penalties, reputational damage, or additional compliance costs. Substantial costs may be incurred in order to prevent any cyber incidents in the future. The Fund and its shareholders could be negatively impacted as a result.

These and other risks are discussed in more detail in “Additional Information About the Funds’ Investment Objectives, Strategies and Risks” in this Prospectus and in the Statement of Additional Information.

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Performance

Performance Narrative [Text Block]

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The bar chart and the average annual total return table below provide some indication of the risks of investing in the Fund by showing how the Fund has performed in the past. The bar chart shows changes in the performance of the Individual Investor Class of the Fund from year to year. The table shows how the average annual total returns of each class of the Fund for 1, 5 and 10 year periods compare with the returns of broad measures of market performance, including the S&P 500 Index and the Custom Balanced Index (the Custom Balanced Index is comprised of a 60% weighting in the S&P 1500 Index and a 40% weighting in the BofA Merrill Lynch 1-10 Year U.S. Corporate & Government Index). The table also compares the performance of each class of the Fund to the Lipper Balanced Fund Index, a universe of mutual funds with investment objectives similar to that of the Fund.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available on the Fund’s website, www.greencentury.com/fund-performance/, or by calling 1-800-934-7336.

Performance Information Illustrates Variability of Returns [Text]

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Performance Additional Market Index [Text]

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The table also compares the performance of each class of the Fund to the Lipper Balanced Fund Index, a universe of mutual funds with investment objectives similar to that of the Fund.

Performance Availability Phone [Text]

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1-800-934-7336

Performance Availability Website Address [Text]

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www.greencentury.com/fund-performance/

Performance Past Does Not Indicate Future [Text]

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The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

Bar Chart [Heading]

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Annual Total Returns for Years Ended December 31 Green Century Balanced Fund – Individual Investor Class

Bar Chart Closing [Text Block]

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During the period shown, the Fund’s Individual Investor Class best quarterly performance was 14.28%, for the quarter ended 6/30/20. The Fund’s Individual Investor Class worst quarterly performance was -12.74%, for the quarter ended 3/31/20.

As of September 30, 2022, the year-to-date return for the Fund’s Individual Investor Class was -20.56%.

Performance Table Heading

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Average Annual Total Returns For the Periods Ended December 31, 2021

Performance Table Uses Highest Federal Rate

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The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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The after-tax returns are shown for the Individual Investor Class of the Fund and the after-tax returns for the Institutional Class of the Fund will vary.

Performance Table Narrative

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Institutional Shares were offered as of November 28, 2020. The Institutional Class performance prior to November 28, 2020 reflects the performance of the Fund’s Individual Investor Class. The after-tax returns are shown for the Individual Investor Class of the Fund and the after-tax returns for the Institutional Class of the Fund will vary. The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts.

GREEN CENTURY BALANCED FUND | Individual Investor Class

Maximum Sales Charge (Load) Imposed on Purchases

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none

Maximum Deferred Sales Charge (Load)

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none

Redemption Fee (as a percentage of an amount redeemed within 60 days of purchase)

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2.00%

Wire Redemption Fee (if such services are requested)

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$ 10

Overnight Delivery Fee (if such services are requested)

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$ 30

Management Fees

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0.63%

Distribution (12b-1) Fees

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none

Administrative Fees

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0.83%

Other Fees

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none

Total Annual Fund Operating Expenses

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1.46%

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$ 149

3 Years

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462

rr_ExpenseExampleYear05

797

Year to Date Return, Label

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$ 1,746

2012

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13.29%

2013

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23.67%

2014

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7.20%

2015

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(1.35%)

2016

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5.39%

2017

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12.78%

2018

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(2.14%)

2019

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20.91%

2020

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15.95%

2021

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16.43%

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year-to-date return

Bar Chart, Year to Date Return, Date

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Sep. 30, 2022

Bar Chart, Year to Date Return

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(20.56%)

Highest Quarterly Return, Label

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best quarterly performance

Highest Quarterly Return, Date

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Jun. 30, 2020

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.28%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

worst quarterly performance

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2020

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(12.74%)

rr_AverageAnnualReturnYear01

16.43%

rr_AverageAnnualReturnYear05

12.49%

rr_AverageAnnualReturnYear10

10.90%

rr_AverageAnnualReturnSinceInception

7.66%

GREEN CENTURY BALANCED FUND | Institutional Class

rr_AverageAnnualReturnInceptionDate

Mar. 18, 1992

Maximum Sales Charge (Load) Imposed on Purchases

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption Fee (as a percentage of an amount redeemed within 60 days of purchase)

rr_RedemptionFeeOverRedemption

2.00%

Wire Redemption Fee (if such services are requested)

gcf_WireRedemptionFeeIfSuchServicesAreRequested

$ 10

Overnight Delivery Fee (if such services are requested)

gcf_OvernightDeliveryFeeIfSuchServicesAreRequested

$ 30

Management Fees

rr_ManagementFeesOverAssets

0.63%

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Administrative Fees

rr_Component1OtherExpensesOverAssets

0.53%

Other Fees

rr_Component2OtherExpensesOverAssets

none

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.16%

rr_ExpenseExampleYear01

$ 118

3 Years

rr_ExpenseExampleYear03

368

rr_ExpenseExampleYear05

638

rr_ExpenseExampleYear10

$ 1,409

rr_AverageAnnualReturnYear01

16.74%

rr_AverageAnnualReturnYear05

12.57%

rr_AverageAnnualReturnYear10

10.93%

rr_AverageAnnualReturnSinceInception

7.67%

GREEN CENTURY BALANCED FUND | Return after taxes on distributions | Individual Investor Class

rr_AverageAnnualReturnInceptionDate

Mar. 18, 1992

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

15.36%

rr_AverageAnnualReturnYear05

11.78%

rr_AverageAnnualReturnYear10

10.26%

rr_AverageAnnualReturnSinceInception

6.82%

GREEN CENTURY BALANCED FUND | Return after taxes on distributions and sale of Fund shares | Individual Investor Class

rr_AverageAnnualReturnInceptionDate

Mar. 18, 1992

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

10.49%

rr_AverageAnnualReturnYear05

9.87%

rr_AverageAnnualReturnYear10

8.88%

rr_AverageAnnualReturnSinceInception

6.26%

GREEN CENTURY BALANCED FUND | Custom Balanced Index (reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnInceptionDate

Mar. 18, 1992

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

15.81%

rr_AverageAnnualReturnYear05

12.05%

rr_AverageAnnualReturnYear10

10.83%

rr_AverageAnnualReturnSinceInception

GREEN CENTURY BALANCED FUND | Lipper Balanced Fund Index (reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnInceptionDate

Mar. 18, 1992

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

13.18%

rr_AverageAnnualReturnYear05

10.80%

rr_AverageAnnualReturnYear10

9.55%

rr_AverageAnnualReturnSinceInception

7.79%

GREEN CENTURY BALANCED FUND | S&P 500 Index (reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnInceptionDate

Mar. 18, 1992

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

28.71%

rr_AverageAnnualReturnYear05

18.47%

rr_AverageAnnualReturnYear10

16.55%

rr_AverageAnnualReturnSinceInception

10.78%