Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Central Index Key	dei_EntityCentralIndexKey	0001342947
BBH Partner Fund - Small Cap Equity
Risk/Return:	rr_RiskReturnAbstract
Risk/Return, Heading	rr_RiskReturnHeading	BBH PARTNER FUND—SMALL CAP EQUITY SUMMARY
Investment Objective, Heading	rr_ObjectiveHeading	INVESTMENT OBJECTIVE The investment objective of the BBH Partner Fund—Small Cap Equity (the “Fund”) is to provide investors with long-term growth of capital.
Investment Objective, Primary	rr_ObjectivePrimaryTextBlock	The investment objective of the BBH Partner Fund—Small Cap Equity (the “Fund”) is to provide investors with long-term growth of capital.
Expense, Heading	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense, Narrative	rr_ExpenseNarrativeTextBlock	The table below describes the fees and expenses that you may pay if you buy, hold, and sell the Fund’s Class I Shares. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and expense example below.
Shareholder Fees, Caption	rr_ShareholderFeesCaption	Shareholder Fees (Fees paid directly from your investment)
Operating Expenses, Caption	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover, Heading	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover	rr_PortfolioTurnoverTextBlock	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 above, affect the Fund’s performance. For the period from July 8, 2021 (the Fund’s commencement of operations) to October 31, 2021, the Fund’s portfolio turnover rate was 3% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	3.00%
Expense Example, Heading	rr_ExpenseExampleHeading	EXAMPLE
Expense Example, Narrative	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund’s shares to the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund’s shares for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund’s shares remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Investment Strategy, Heading	rr_StrategyHeading	PRINCIPAL INVESTMENT STRATEGIES
Investment Strategy, Narrative	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small cap equity securities. Such securities will be publicly traded and issued by domestic issuers directly. The Fund primarily seeks to purchase common stock. The Fund considers small cap securities to be securities that at the time of purchase have market capitalizations between (or equal) to the largest and smallest companies within the Russell 2000 Index and/or are constituents of the Russell 2000 Index, as of the date of the latest reconstitution. As of January 31, 2022, the market capitalization range of companies included in the Russell 2000 Index was 4 $22.0 million to $10.1 billion. The Fund will concentrate at least 25% of its net assets in the Software & Services Industry Group within the Information Technology Sector. Brown Brothers Harriman & Co. (“BBH&Co.”), through a separately identifiable department (“Investment Adviser”), employs a “manager of managers” investment approach, whereby it allocates the Fund’s assets to the Fund’s sub-adviser, Bares Capital Management, Inc. (“Sub-adviser”). Subject to the general supervision by the Fund’s Board of Trustees (“Board”), the Investment Adviser oversees the Sub-adviser and evaluates its performance results. The Investment Adviser reviews portfolio performance, characteristics and changes in key personnel of the Sub-adviser. The Sub-adviser is primarily responsible for the day-to-day management of the Fund’s portfolio, including purchases and sales of individual securities. However, the Investment Adviser may, when deemed appropriate, manage all or a portion of the Fund’s assets according to the Fund’s principal investment strategies. The Sub-adviser focuses on identifying companies that it believes are qualitatively excellent through “bottoms-up” research, primarily involving a review of public documents; field work, including company site visits, industry trade shows, user conferences and product demonstrations; discussions with suppliers, customers and competitors; and other primary and secondary due diligence. The Fund will typically invest in companies with durable competitive advantages; the potential for high returns on invested capital; skilled, shareholder-friendly management teams; and large growth opportunities. After qualitative assessment is complete, the Sub-adviser values the companies that meet its criteria using a discounted cash flow model or other relevant methods and invests in a limited number of companies that present the most compelling mix of qualitative characteristics (e.g., competitive position) and quantitative metrics (e.g., price in relation to intrinsic value). As part of the Fund’s investment process, the Sub-adviser considers environmental, social and governance (“ESG”) factors for each investment in the portfolio. ESG factors include, but are not limited to, the environmental and social impact of the issuer, as well as the issuer’s instituted governance programs. Investments may be sold if they appreciate to levels at or near the higher end of the Sub-adviser’s estimated 5 ranges of intrinsic value. However, the Fund may retain these investments if they continue to meet the Fund’s investment objective and strategy. The Fund operates as a “non-diversified company” under the Investment Company Act of 1940 (the “1940 Act”), which means that the Fund may invest a significant portion of its assets in the securities of a limited number of issuers. The Fund invests in at least 20 companies, each of which must meet the Sub-adviser's prescriptive fundamental criteria.
Strategy Portfolio Concentration	rr_StrategyPortfolioConcentration	Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small cap equity securities. Such securities will be publicly traded and issued by domestic issuers directly. The Fund primarily seeks to purchase common stock. The Fund considers small cap securities to be securities that at the time of purchase have market capitalizations between (or equal) to the largest and smallest companies within the Russell 2000 Index and/or are constituents of the Russell 2000 Index, as of the date of the latest reconstitution. As of January 31, 2022, the market capitalization range of companies included in the Russell 2000 Index was
Risk, Heading	rr_RiskHeading	PRINCIPAL RISKS OF THE FUND
Risk, Narrative	rr_RiskNarrativeTextBlock	The principal risks of investing in the Fund and the circumstances reasonably likely to adversely affect an investment are listed and described below. The share price of the Fund changes daily, based on market conditions and other factors. A shareholder may lose money by investing in the Fund. There can be no assurance that the Fund will achieve its investment objective. Small Cap Company Risk: Small cap companies, when compared to larger companies, may experience lower trade volume and could be subject to greater and less predictable price changes. Small cap companies may also have limited management experience or depth, limited ability to generate or borrow capital needed for growth, limited products or services, or operate in less established markets. Therefore, small cap securities may be subject to changing economic, market, and industry conditions and experience more volatility and less liquidity over short periods. 6 Investment Risk: Investors in the Fund could lose money, including the possible loss of the entire principal amount of an investment, over short or long periods of time. Market Risk: The price of a security may fall due to changing economic, political, regulatory or market conditions, or due to a company’s or issuer’s individual situation. Natural disasters, the spread of infectious illness and other public health emergencies, recession, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse effects on world economies and markets generally. Equity Securities Risk: Equity securities risk is the risk that prices of equity securities rise and fall daily. Price movements may occur due to factors affecting individual companies, such as the issuance of an unfavorable earnings report, or other events affecting particular industries or the equity market as a whole. Non-Diversification Risk: Because a non-diversified fund under the federal securities laws may invest in a relatively small number of issuers compared to a diversified fund, changes in the financial condition of individual issuers, as well as political, regulatory or economic occurrences affecting such issuers may cause greater fluctuation in the value of a non-diversified fund’s shares. However, the Fund intends to satisfy the asset diversification requirements for qualification as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”). Software & Services Industry Group Concentration Risk: When a fund focuses its investments in a particular industry, group of industries, or sector, financial, economic, business, and other developments affecting issuers in those industries or sector will have a greater effect on the fund than if it had not done so. Market or economic factors impacting 7 companies in the information technology sector could have a major effect on the value of the Fund’s investments. Stocks of such companies, especially those of smaller, less-seasoned companies, tend to be more volatile than the overall market. Additionally, companies in the information technology sector may face unpredictable changes in growth rates and competition for the services of qualified personnel. Computer software/services companies can be significantly affected by competitive pressures, aggressive pricing, technological developments, changing domestic demand, the ability to attract and retain skilled employees and availability and price of components. The market for products produced by computer software/services companies is characterized by rapidly changing technology, evolving industry standards and frequent new product introductions. The success of computer software/services companies depends in substantial part on the timely and successful introduction of new products and the ability to service such products. An unexpected change in one or more of the technologies affecting an issuer’s products or in the market for products based on a particular technology could have a material adverse effect on a participant’s operating results. Some computer software/services companies rely on a combination of patents, copyrights, trademarks and trade secret laws to establish and protect their proprietary rights in their products and technologies. There can be no assurance that the steps taken by computer software/services companies to protect their proprietary rights will be adequate to prevent misappropriation of their technology or that competitors will not independently develop technologies that are substantially equivalent or superior to such companies’ technology. 8 Large Shareholder Risk: Asset allocation decisions, particularly large redemptions, made by an investor or an investment adviser whose discretionary clients make up a large percentage of the Fund’s shareholders, may adversely impact remaining Fund shareholders. Management Risk: The Fund is actively managed, and its success depends upon the investment skills and analytical abilities of the Sub-adviser to develop and effectively implement strategies that achieve the Fund’s investment objective. Subjective decisions made by the Sub-adviser may cause the Fund to incur losses or to miss profit opportunities on which it may otherwise have capitalized.
Risk, Lose Money	rr_RiskLoseMoney	A shareholder may lose money by investing in the Fund.
Risk, Nondiversified Status	rr_RiskNondiversifiedStatus	Non-Diversification Risk: Because a non-diversified fund under the federal securities laws may invest in a relatively small number of issuers compared to a diversified fund, changes in the financial condition of individual issuers, as well as political, regulatory or economic occurrences affecting such issuers may cause greater fluctuation in the value of a non-diversified fund’s shares. However, the Fund intends to satisfy the asset diversification requirements for qualification as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”).
Bar Chart and Performance Table, Heading	rr_BarChartAndPerformanceTableHeading	FUND PERFORMANCE
Performance, Narrative	rr_PerformanceNarrativeTextBlock	The Fund commenced investment operations on July 8, 2021 and, therefore, does not have performance history for a full calendar year. Once the Fund has completed a full calendar year of operations, performance information will be indicative of the risks of investing in the Fund by comparing the Fund’s performance relative to the Fund’s benchmark index and peer group.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund commenced investment operations on July 8, 2021 and, therefore, does not have performance history for a full calendar year. Once the Fund has completed a full calendar year of operations, performance information will be indicative of the risks of investing in the Fund by comparing the Fund’s performance relative to the Fund’s benchmark index and peer group.
BBH Partner Fund - Small Cap Equity \| Class I Shares
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee on shares held less than 30 days after purchase (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	2.00%
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.93%
1 Year	rr_ExpenseExampleYear01	$ 95
3 Years	rr_ExpenseExampleYear03	297
5 Years	rr_ExpenseExampleYear05	515
10 Years	rr_ExpenseExampleYear10	$ 1,144

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Central Index Key

dei_EntityCentralIndexKey

0001342947

BBH Partner Fund - Small Cap Equity

Risk/Return:

rr_RiskReturnAbstract

Risk/Return, Heading

rr_RiskReturnHeading

BBH PARTNER FUND—SMALL CAP EQUITY SUMMARY

Investment Objective, Heading

rr_ObjectiveHeading

INVESTMENT OBJECTIVE The investment objective of the BBH Partner Fund—Small Cap Equity (the “Fund”) is to provide investors with long-term growth of capital.

Investment Objective, Primary

rr_ObjectivePrimaryTextBlock

The investment objective of the BBH Partner Fund—Small Cap Equity (the “Fund”) is to provide investors with long-term growth of capital.

Expense, Heading

rr_ExpenseHeading

FEES AND EXPENSES OF THE FUND

Expense, Narrative

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy, hold, and sell the Fund’s Class I Shares. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and expense example below.

Shareholder Fees, Caption

rr_ShareholderFeesCaption

Shareholder Fees (Fees paid directly from your investment)

Operating Expenses, Caption

rr_OperatingExpensesCaption

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

Portfolio Turnover, Heading

rr_PortfolioTurnoverHeading

Portfolio Turnover

rr_PortfolioTurnoverTextBlock

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 above, affect the Fund’s performance. For the period from July 8, 2021 (the Fund’s commencement of operations) to October 31, 2021, the Fund’s portfolio turnover rate was 3% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

3.00%

Expense Example, Heading

rr_ExpenseExampleHeading

EXAMPLE

Expense Example, Narrative

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund’s shares to the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund’s shares for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund’s shares remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Investment Strategy, Heading

rr_StrategyHeading

PRINCIPAL INVESTMENT STRATEGIES

Investment Strategy, Narrative

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small cap equity securities. Such securities will be publicly traded and issued by domestic issuers directly. The Fund primarily seeks to purchase common stock. The Fund considers small cap securities to be securities that at the time of purchase have market capitalizations between (or equal) to the largest and smallest companies within the Russell 2000 Index and/or are constituents of the Russell 2000 Index, as of the date of the latest reconstitution. As of January 31, 2022, the market capitalization range of companies included in the Russell 2000 Index was

$22.0 million to $10.1 billion. The Fund will concentrate at least 25% of its net assets in the Software & Services Industry Group within the Information Technology Sector.

Brown Brothers Harriman & Co. (“BBH&Co.”), through a separately identifiable department (“Investment Adviser”), employs a “manager of managers” investment approach, whereby it allocates the Fund’s assets to the Fund’s sub-adviser, Bares Capital Management, Inc. (“Sub-adviser”). Subject to the general supervision by the Fund’s Board of Trustees (“Board”), the Investment Adviser oversees the Sub-adviser and evaluates its performance results. The Investment Adviser reviews portfolio performance, characteristics and changes in key personnel of the Sub-adviser. The Sub-adviser is primarily responsible for the day-to-day management of the Fund’s portfolio, including purchases and sales of individual securities. However, the Investment Adviser may, when deemed appropriate, manage all or a portion of the Fund’s assets according to the Fund’s principal investment strategies.

The Sub-adviser focuses on identifying companies that it believes are qualitatively excellent through “bottoms-up” research, primarily involving a review of public documents; field work, including company site visits, industry trade shows, user conferences and product demonstrations; discussions with suppliers, customers and competitors; and other primary and secondary due diligence. The Fund will typically invest in companies with durable competitive advantages; the potential for high returns on invested capital; skilled, shareholder-friendly management teams; and large growth opportunities. After qualitative assessment is complete, the Sub-adviser values the companies that meet its criteria using a discounted cash flow model or other relevant methods and invests in a limited number of companies that present the most compelling mix of qualitative characteristics (e.g., competitive position) and quantitative metrics (e.g., price in relation to intrinsic value). As part of the Fund’s investment process, the Sub-adviser considers environmental, social and governance (“ESG”) factors for each investment in the portfolio. ESG factors include, but are not limited to, the environmental and social impact of the issuer, as well as the issuer’s instituted governance programs. Investments may be sold if they appreciate to levels at or near the higher end of the Sub-adviser’s estimated

ranges of intrinsic value. However, the Fund may retain these investments if they continue to meet the Fund’s investment objective and strategy.

The Fund operates as a “non-diversified company” under the Investment Company Act of 1940 (the “1940 Act”), which means that the Fund may invest a significant portion of its assets in the securities of a limited number of issuers. The Fund invests in at least 20 companies, each of which must meet the Sub-adviser's prescriptive fundamental criteria.

Strategy Portfolio Concentration

rr_StrategyPortfolioConcentration

Risk, Heading

rr_RiskHeading

PRINCIPAL RISKS OF THE FUND

Risk, Narrative

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund and the circumstances reasonably likely to adversely affect an investment are listed and described below. The share price of the Fund changes daily, based on market conditions and other factors. A shareholder may lose money by investing in the Fund. There can be no assurance that the Fund will achieve its investment objective.

Small Cap Company Risk:

Small cap companies, when compared to larger companies, may experience lower trade volume and could be subject to greater and less predictable price changes. Small cap companies may also have limited management experience or depth, limited ability to generate or borrow capital needed for growth, limited products or services, or operate in less established markets. Therefore, small cap securities may be subject to changing economic, market, and industry conditions and experience more volatility and less liquidity over short periods.

Investment Risk:

Investors in the Fund could lose money, including the possible loss of the entire principal amount of an investment, over short or long periods of time.

Market Risk:

The price of a security may fall due to changing economic, political, regulatory or market conditions, or due to a company’s or issuer’s individual situation. Natural disasters, the spread of infectious illness and other public health emergencies, recession, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse effects on world economies and markets generally.

Equity Securities Risk:

Equity securities risk is the risk that prices of equity securities rise and fall daily. Price movements may occur due to factors affecting individual companies, such as the issuance of an unfavorable earnings report, or other events affecting particular industries or the equity market as a whole.

Non-Diversification Risk:

Because a non-diversified fund under the federal securities laws may invest in a relatively small number of issuers compared to a diversified fund, changes in the financial condition of individual issuers, as well as political, regulatory or economic occurrences affecting such issuers may cause greater fluctuation in the value of a non-diversified fund’s shares. However, the Fund intends to satisfy the asset diversification requirements for qualification as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”).

Software & Services Industry Group Concentration Risk:

When a fund focuses its investments in a particular industry, group of industries, or sector, financial, economic, business, and other developments affecting issuers in those industries or sector will have a greater effect on the fund than if it had not done so. Market or economic factors impacting

companies in the information technology sector could have a major effect on the value of the Fund’s investments. Stocks of such companies, especially those of smaller, less-seasoned companies, tend to be more volatile than the overall market. Additionally, companies in the information technology sector may face unpredictable changes in growth rates and competition for the services of qualified personnel.

Computer software/services companies can be significantly affected by competitive pressures, aggressive pricing, technological developments, changing domestic demand, the ability to attract and retain skilled employees and availability and price of components. The market for products produced by computer software/services companies is characterized by rapidly changing technology, evolving industry standards and frequent new product introductions. The success of computer software/services companies depends in substantial part on the timely and successful introduction of new products and the ability to service such products. An unexpected change in one or more of the technologies affecting an issuer’s products or in the market for products based on a particular technology could have a material adverse effect on a participant’s operating results. Some computer software/services companies rely on a combination of patents, copyrights, trademarks and trade secret laws to establish and protect their proprietary rights in their products and technologies. There can be no assurance that the steps taken by computer software/services companies to protect their proprietary rights will be adequate to prevent misappropriation of their technology or that competitors will not independently develop technologies that are substantially equivalent or superior to such companies’ technology.

Large Shareholder Risk:

Asset allocation decisions, particularly large redemptions, made by an investor or an investment adviser whose discretionary clients make up a large percentage of the Fund’s shareholders, may adversely impact remaining Fund shareholders.

Management Risk:

The Fund is actively managed, and its success depends upon the investment skills and analytical abilities of the Sub-adviser to develop and effectively implement strategies that achieve the Fund’s investment objective. Subjective decisions made by the Sub-adviser may cause the Fund to incur losses or to miss profit opportunities on which it may otherwise have capitalized.

Risk, Lose Money

rr_RiskLoseMoney

A shareholder may lose money by investing in the Fund.

Risk, Nondiversified Status

rr_RiskNondiversifiedStatus

Non-Diversification Risk: Because a non-diversified fund under the federal securities laws may invest in a relatively small number of issuers compared to a diversified fund, changes in the financial condition of individual issuers, as well as political, regulatory or economic occurrences affecting such issuers may cause greater fluctuation in the value of a non-diversified fund’s shares. However, the Fund intends to satisfy the asset diversification requirements for qualification as a regulated investment company (“RIC”) under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”).

Bar Chart and Performance Table, Heading

rr_BarChartAndPerformanceTableHeading

FUND PERFORMANCE

Performance, Narrative

rr_PerformanceNarrativeTextBlock

The Fund commenced investment operations on July 8, 2021 and, therefore, does not have performance history for a full calendar year. Once the Fund has completed a full calendar year of operations, performance information will be indicative of the risks of investing in the Fund by comparing the Fund’s performance relative to the Fund’s benchmark index and peer group.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

BBH Partner Fund - Small Cap Equity | Class I Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Maximum Sales Charge (Load) Imposed on Reinvested Dividends