v3.26.1
Inflation Managed Portfolio Investment Risks - Inflation Managed 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 and the adviser’s quality determinations with respect to securities that are unrated by the major credit rating agencies may be inaccurate, which could cause the Portfolio to underperform other mutual funds or lose money.
Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Counterparty Risk – The Portfolio may sustain a loss in the event the other party(s) in an agreement or a participant to a transaction, such as a broker or swap counterparty, defaults on a contract or fails to perform by failing to pay amounts due, failing to fulfill delivery conditions, or failing to otherwise comply with the terms of the contract. Counterparty risk is inherent in many transactions, including derivatives transactions.
Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Credit Risk – The Portfolio could lose money if the issuer or guarantor of a fixed income security is unwilling or unable to meet its financial obligations. In addition, changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Portfolio’s investment in that issuer. Changes in credit spreads or improvements in an issuer’s credit quality may increase the risk that an issuer calls outstanding securities prior to their maturity.
Debt Obligations of Foreign Governments Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Debt Obligations of Foreign Governments Risk – The issuer of the foreign debt or the governmental authorities that control the repayment of such debt may be unable or unwilling to repay principal or interest when due, and the Portfolio may have limited recourse in the event of a default. The market prices of debt obligations of governments and their agencies, and the Portfolio’s net asset value, may be more volatile than prices of U.S. debt obligations. In addition, unlike debt instruments issued by the U.S. Treasury, inflation-linked bonds issued by corporations or foreign governments do not generally provide principal protection, and in a deflationary environment, such bonds may result in the loss of principal.
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 primary risks associated with the Portfolio’s use of derivatives are the risk the risk that changes in the value of the derivatives may not correlate as intended with the underlying asset, rate or index, the risk that the counterparty to a derivatives transaction fails to make the required payment, the risk of missed opportunities in other investments, and the risk of adverse price movements in the market. Certain derivatives involve leverage, which could cause the Portfolio to lose more than the principal amount invested. Other risks include management, interest rate, liquidity risks and the risk of missed opportunities in other investments. The Portfolio's purchase of swap agreements may pose risk arising from losses if the underlying reference asset does not perform as anticipated; such agreements are also subject to counterparty credit, liquidity and leveraging risks.
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.
Foreign Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Foreign Currency Risk – The risk that foreign (non-U.S. dollar) currency denominated securities, or derivatives that provide exposure to foreign currencies, 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.
Forward Foreign Currency Exchange Contracts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Forward Foreign Currency Exchange Contracts Risk – Forward foreign currency exchange contracts are OTC contracts to purchase or sell a specified amount of a specified currency at a price and future date set at the time of the contract. Forward foreign currency exchange contracts do not eliminate fluctuations in the value of non-U.S. securities but rather allow the Fund to establish a fixed rate of exchange for a future point in time. This strategy can have the effect of reducing returns and minimizing opportunities for gain.  Engaging in forward foreign currency exchange contracts will subject the Fund to counterparty credit risk and any failure to perform by a counterparty could result in a loss to the Fund.
Inflation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Inflation Risk – Your investment in the Portfolio may not provide enough income to keep pace with inflation. To the extent that the Portfolio holds investments in non-inflation-linked debt securities, as noted above, that portion of the Portfolio will not be automatically protected from inflation.
Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Interest Rate Risk – Prices of fixed income instruments, including inflation-indexed debt securities, generally rise and fall in response to changes in market interest rates. In a rising interest rate environment, the value of the Portfolio’s fixed income investments is likely to decline. A significant rise in interest rates over a short period of time could cause significant losses in the market value of the Portfolio’s fixed income instruments. A portfolio with a longer average portfolio duration will be more
sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration. For example, the market value of a fixed income portfolio with an average duration of five years generally would be expected to fall approximately 5% if interest rates rose by one percentage point. Declining interest rates may increase the risk that an issuer calls outstanding securities prior to their maturity.
Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Liquidity Risk – Fixed income and derivative investments can be difficult to purchase or sell at an advantageous time or price, if at all, during periods of reduced marketability for the investment or due to the size of the transaction. These risks may be magnified during periods of economic turmoil or in an extended economic downturn or when investing in emerging markets.
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.
Mortgage-and Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Mortgage- and Asset-Backed Securities Risk – The Portfolio invests in collateralized mortgage obligations, mortgage-backed securities, including commercial mortgage-backed securities, collateralized loan obligations, and asset-backed securities. Mortgage-related and other asset-backed securities are subject to interest rate risk, credit risk and liquidity risk as well as additional risks including prepayment and extension risk. Mortgage-related and other asset-backed securities represent interests in pools of mortgages or other assets and often involve risks that are different or possibly more acute than risks associated with other types of debt instruments. The value of some mortgage- or asset-backed securities may be particularly sensitive to changes in prevailing interest rates. Mortgage-backed securities offered by non-governmental issuers are subject to specific risks, such as the failure of private insurers to meet their obligations and unexpectedly high rates of default on the mortgages backing the securities. Other asset-backed securities are subject to risks similar to those associated with mortgage-backed securities, as well as risks associated with the nature and servicing of the assets underlying the securities. Asset-backed securities may not have the benefit of a security interest in collateral comparable to that of mortgage assets, resulting in additional credit risk.
Prepayment and Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •Prepayment and Extension Risk – Prepayment risk is the risk that principal on a debt obligation will be paid earlier than scheduled or expected, which could reduce yield and market value of the security and shorten the Portfolio’s average effective maturity. The rate of prepayments tends to increase as interest rates fall. Extension risk is the risk that, as interest rates rise, repayments on a debt obligation may occur more slowly than anticipated by the market and the obligation may remain outstanding longer.
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.
U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] •U.S. Government Securities Risk – Not all obligations of the U.S. government, its agencies and instrumentalities are backed by the full faith and credit of the U.S. Treasury. Some obligations are backed only by the credit of the issuing agency or instrumentality, and in some cases there may be some risk of default by the issuer. Any guarantee by the U.S. government or its agencies or instrumentalities of a security held by the Portfolio does not apply to the market value of such security or to shares of the Portfolio itself.
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 and there is no guarantee of inflation protection.