v3.26.1
International Equity Portfolio Investment Risks - International Equity Portfolio
Dec. 31, 2025
Active Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Active Management Risk – The adviser’s investment strategies and techniques may not perform as expected which could cause the Portfolio to underperform other mutual funds or lose money.
ADR Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •ADR Risk – ADRs are receipts representing ownership of shares of a foreign issuer held by a U.S. bank or similar financial institution that entitle the holder to dividends and capital gains on the underlying foreign shares. ADRs are alternatives to directly purchasing the underlying foreign securities in their national markets and currencies. They, and other similar depositary receipts, are subject to many of the risks associated with direct investments in foreign securities, such as currency risk, political and economic risk and market risk, because their values depend on the performance of the non-dollar denominated underlying foreign securities. The Portfolio is also subject to fees and the credit risk of the financial institution holding the ADRs or other depositary receipts. ADRs may be “sponsored,” meaning that they are implemented by a financial institution in collaboration with the issuing foreign company, or “unsponsored,” meaning that the financial institution created the instrument without the sponsorship or direct involvement of the foreign company. Differing registration requirements apply to each type of ADR. ADRs may transact on exchanges or on over-the-counter markets (“OTC”). Conducting transactions in OTC markets may result in higher costs, a lack of pricing transparency and lower liquidity when compared with exchange-based transactions. Risks associated with different ADR types will vary, based upon differences in registration, reporting and disclosure requirements that apply to such ADRs and the characteristics of the market in which transactions for the particular ADR are conducted.
Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Derivatives Risk – The value of a derivative generally depends upon, or is derived from, an underlying asset, reference rate or index. The Portfolio’s use of derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities or other traditional investments. Investments in derivatives may not have the intended effects and may result in losses for the Portfolio that may not otherwise have occurred or missed opportunities for the Portfolio. Certain derivatives involve leverage, which could cause the Portfolio to lose more than the principal amount invested. The derivatives could involve management, credit, interest rate, liquidity and market risks, and the risks of misplacing or improper valuation. Changes in the value of the derivative may not correlate as intended with the underlying asset, rate or index. In addition, the Portfolio could sustain a loss in the event the counterparty to a derivatives transaction fails to make the required payments or otherwise comply with the terms of the contract. The Portfolio’s purchase of forwards contracts may involve risks related to imperfect correlation between the prices of such instruments and the price of the underlying asset, as well as leverage, liquidity and volatility risks. In addition, the purchase of forwards also involves counterparty credit risk as well as heightened market risk.
Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Emerging Markets Risk – Investing in emerging market securities increases foreign investing risk, and may subject the Portfolio to more rapid and extreme changes in the value of its holdings compared with investments made in U.S. securities or in foreign, developed countries. Investments in emerging markets may be subject to political, economic, legal, market, and currency risks. Emerging market securities trade in smaller markets which may experience significant price and market volatility, fluctuations in currency values, interest rates and commodity prices, higher transaction costs, and the increased likelihood of the occurrence of trading difficulties, such as delays in executing, clearing and settling Portfolio transactions or in receiving payment of dividends. Special risks associated with investments in emerging market issuers may include a lack of publicly available information, a lack of uniform disclosure, accounting, financial reporting, and recordkeeping standards, and more limited investor protection provisions when compared with developed economies. Emerging market risks also may include unpredictable and changing political, economic and tax policies, the imposition of capital controls and/or foreign investment limitations by a country, nationalization of businesses, and the imposition of sanctions or restrictions in certain investments by other countries, such as the United States.
Equity Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Equity Securities Risk – The value of equity securities, such as common stocks, could decline if the financial condition of the companies the Portfolio is invested in declines or if overall market and economic conditions deteriorate. Equity securities generally have greater price volatility than fixed income securities.
ESG Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •ESG Risk – Incorporating the consideration of ESG factors in the investment process may affect the Portfolio’s exposure to certain issuers or industries and may not work as intended. The Portfolio may underperform other funds that do not consider ESG factors or that use different ESG factors to evaluate a security. Information used to evaluate ESG factors may not be readily available, complete, or accurate, and may vary across providers and issuers, as ESG factors are not uniformly defined or assessed. There is no guarantee that evaluating ESG considerations for individual securities will positively contribute to the Portfolio’s performance results.
Foreign Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Foreign Currency Risk – The risk that foreign (non-U.S. dollar) currency denominated securities may be adversely affected by decreases in foreign currency values relative to the U.S. dollar. Investments in securities subject to foreign currency risk may have more rapid and extreme changes in value or more losses than investments in U.S. dollar denominated securities.
Foreign Investing Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Foreign Investing Risk – Investing in foreign securities may subject the Portfolio to more rapid and extreme changes in value or more losses than a fund that invests exclusively in U.S. securities. This risk is due to potentially smaller markets, differing reporting, accounting and auditing standards, and nationalization, expropriation or confiscatory taxation, currency blockage, political and economic conditions, or diplomatic developments. Foreign securities may be less liquid, more volatile, and harder to value than U.S. securities.
Geographic Focus Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Geographic Focus Risk – The Portfolio’s performance could be more volatile than that of a more geographically diversified fund and could be significantly impacted as a result of the Portfolio investing a relatively large percentage of its assets in issuers located in a single country, a small number of countries, or a particular geographic region. Also, the Portfolio’s performance may be more closely tied to the market, currency, economic, political, or regulatory conditions in those countries or that region.
Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Investment Style Risk – A portfolio managed using a value style of investing, such as the Portfolio, may underperform when the market does not favor the particular style used by the Portfolio. Different investment styles tend to shift in and out of favor, depending on market conditions and investor sentiment.
Large Cap Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Large Cap Company Risk – Investing in large cap stocks could cause the Portfolio to underperform in markets favoring faster growing companies. Large cap stocks tend to be more mature with fewer opportunities to grow and may not have the same growth potential as stocks with smaller capitalizations.
Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Liquidity Risk – Markets for foreign securities, in particular emerging markets securities, may be less liquid than markets for larger cap stocks and domestic securities, and therefore may be difficult to purchase or sell at an advantageous time or price, if at all. These risks may be magnified during periods of economic turmoil or in an extended economic downturn.
Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Market Risk – The risk that the market price of securities owned by the Portfolio may go up or down, sometimes rapidly or unpredictably. The value of a security may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Global economies and financial markets are increasingly interconnected, which magnifies the potential that conditions in one country or region might adversely impact issuers in, or foreign exchange rates with, a different country or region. Geopolitical and other events, including war, terrorism, economic uncertainty, trade disputes, tariffs, public health crises (such as epidemics and pandemics), and related events have led, and in the future may lead, to increased market volatility, which may disrupt U.S. and world economies and markets and may have significant adverse direct or indirect effects on the Portfolio and its investments.
Mid Cap Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Mid Cap Company Risk – Investing in mid cap stocks may cause greater risk of loss and price fluctuation than investing in stocks of larger cap companies due to a more limited track record, narrower product markets, more limited resources and less liquid trading markets. These stocks may be more volatile and more difficult to buy and sell than stocks with larger capitalizations.
Sector Focus Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Sector Focus Risk – To the extent the Portfolio invests a relatively high percentage of its assets in a particular sector, it will have greater exposure to the risks associated with that sector, including the risk that the securities of companies within the sector will underperform due to adverse economic conditions, regulatory or legislative changes, or increased competition affecting the sector. To the extent the Portfolio is underweight in other sectors, the Portfolio risks missing out on advances in those sectors.
Underlying Portfolio Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Underlying Portfolio Risk – The Portfolio may serve as an investment option, or “Underlying Portfolio,” for other portfolios of Northwestern Mutual Series Fund, Inc. that are managed as “fund of funds.” As a result, from time to time, the Portfolio may experience relatively large investments or redemptions from those other portfolios and could be required to invest cash or sell securities at a time when it is not advantageous to do so.
Warrants Investing Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Warrants Investing Risk – Investments in warrants may be more volatile than the underlying common stock and may cause the Portfolio increased risk of loss if the warrants cannot be exercised prudently by the expiration date or if the warrants lack a liquid secondary market for resale. Warrants can provide exposure to an underlying stock for a portion of the price of direct ownership of shares of that stock. As a result, most warrants have some degree of leverage, which can vary depending on the type of warrant. This means that small changes in the value of the underlying stock results in larger changes in the value of the warrant. This can magnify gains when stock prices rise, but it can also magnify losses when stock prices fall.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] Portfolio shares will rise and fall in value and there is a risk you could lose money by investing in the Portfolio. There can be no assurance that the Portfolio will achieve its objective.