The Portfolio invests primarily in companies that are based in emerging and frontier markets. Emerging and frontier markets offer investment opportunities that arise from long-term trends in demographics, deregulation, offshore outsourcing, and improving corporate governance in developing countries. Harding Loevner LP (“Harding Loevner”), the Portfolio’s investment adviser, undertakes fundamental research in an effort to identify companies that are well managed, financially sound, fast growing, and strongly competitive, and whose shares are reasonably priced relative to estimates of their value. To reduce its volatility, the Portfolio is diversified across dimensions of geography, industry, and currency. The Portfolio normally holds investments across at least 15 countries.

Emerging and frontier markets include countries that have an emerging stock market as defined by Morgan Stanley Capital International, countries or markets with low‑to middle-income economies as classified by the World Bank, and other countries or markets with similar characteristics. Emerging and frontier markets tend to have relatively low gross national product per capita compared to the world’s major economies and may have the potential for rapid economic growth.

Factors bearing on whether a company is considered to be “based” in an emerging or frontier market may include: (1) it is legally domiciled in an emerging or frontier market; (2) it conducts at least 50% of its business, as measured by the location of its sales, earnings, assets, or production, in an emerging or frontier market; or (3) it has the principal exchange listing for its securities in an emerging or frontier market.

At least 65% of the Portfolio’s total assets will be denominated in at least three currencies other than the U.S. dollar. For purposes of compliance with this restriction, American Depositary Receipts (“ADRs”), Global Depositary Receipts (“GDRs”), and European Depositary Receipts ( “EDRs”) will be considered to be denominated in the currency of the country where the securities underlying the depositary receipts are principally traded.

The Portfolio invests at least 65% of its total assets in common stocks, preferred stocks, rights, and warrants issued by companies that are based in emerging or frontier markets, securities convertible into such securities (including depositary receipts), and investment companies that invest in the types of securities in which the Portfolio would normally invest. The Portfolio also may invest in securities of U.S. companies that derive, or are expected to derive, a significant portion of their revenues from their foreign operations, although under normal circumstances, not more than 15% of the Portfolio’s total assets will be invested in securities of U.S. companies.

The Portfolio invests, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in emerging markets securities, which includes frontier markets securities, and investment companies that invest in the types of securities in which the Portfolio would normally invest.

Because some emerging market countries may present difficulties for efficient foreign investment, the Portfolio may use equity derivative securities to gain exposure to issuers in those countries.

Institutional [Member] Investment Strategy - Institutional - Harding Loevner Institutional Emerging Markets Portfolio	Oct. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	The Portfolio invests primarily in companies that are based in emerging and frontier markets. Emerging and frontier markets offer investment opportunities that arise from long-term trends in demographics, deregulation, offshore outsourcing, and improving corporate governance in developing countries. Harding Loevner LP (“Harding Loevner”), the Portfolio’s investment adviser, undertakes fundamental research in an effort to identify companies that are well managed, financially sound, fast growing, and strongly competitive, and whose shares are reasonably priced relative to estimates of their value. To reduce its volatility, the Portfolio is diversified across dimensions of geography, industry, and currency. The Portfolio normally holds investments across at least 15 countries. Emerging and frontier markets include countries that have an emerging stock market as defined by Morgan Stanley Capital International, countries or markets with low‑to middle-income economies as classified by the World Bank, and other countries or markets with similar characteristics. Emerging and frontier markets tend to have relatively low gross national product per capita compared to the world’s major economies and may have the potential for rapid economic growth. Factors bearing on whether a company is considered to be “based” in an emerging or frontier market may include: (1) it is legally domiciled in an emerging or frontier market; (2) it conducts at least 50% of its business, as measured by the location of its sales, earnings, assets, or production, in an emerging or frontier market; or (3) it has the principal exchange listing for its securities in an emerging or frontier market. At least 65% of the Portfolio’s total assets will be denominated in at least three currencies other than the U.S. dollar. For purposes of compliance with this restriction, American Depositary Receipts (“ADRs”), Global Depositary Receipts (“GDRs”), and European Depositary Receipts ( “EDRs”) will be considered to be denominated in the currency of the country where the securities underlying the depositary receipts are principally traded. The Portfolio invests at least 65% of its total assets in common stocks, preferred stocks, rights, and warrants issued by companies that are based in emerging or frontier markets, securities convertible into such securities (including depositary receipts), and investment companies that invest in the types of securities in which the Portfolio would normally invest. The Portfolio also may invest in securities of U.S. companies that derive, or are expected to derive, a significant portion of their revenues from their foreign operations, although under normal circumstances, not more than 15% of the Portfolio’s total assets will be invested in securities of U.S. companies. The Portfolio invests, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in emerging markets securities, which includes frontier markets securities, and investment companies that invest in the types of securities in which the Portfolio would normally invest. Because some emerging market countries may present difficulties for efficient foreign investment, the Portfolio may use equity derivative securities to gain exposure to issuers in those countries.