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Loomis Sayles Global Allocation Portfolio Investment Risks - Loomis Sayles Global Allocation Portfolio
Dec. 31, 2025
Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Market Risk.  The Portfolio’s share price can fall because of, among other things, a decline in the market as a whole, deterioration in the prospects for a particular industry or company, changes in general economic conditions, such as prevailing interest rates or investor sentiment, or other factors including terrorism, war, natural disasters and the spread of infectious illness including epidemics or pandemics. In addition, unexpected political, regulatory, trade and diplomatic events within the United States and abroad may affect investor and consumer confidence and may adversely impact financial markets and the broader economy, perhaps suddenly and to a significant degree. Significant disruptions to the financial markets could adversely affect the liquidity and volatility of securities held by the Portfolio.
Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Foreign Investment Risk.  Investments in foreign securities, whether direct or indirect, tend to be more volatile and less liquid than investments in U.S. securities because, among other things, they involve risks relating to political, social, economic and other developments abroad, as well as risks resulting from differences between the regulations and reporting standards and practices to which U.S. and foreign issuers are subject. To the extent foreign securities are denominated in foreign currencies, their values may be adversely affected by changes in currency exchange rates. To the extent the Portfolio invests in foreign sovereign debt securities, it is subject to additional risks.
Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Emerging Markets Risk.  In addition to all of the risks of investing in foreign developed markets, emerging market securities involve risks attendant to less mature and stable governments and economies, lower trading volume, trading suspension, security price volatility, proceeds repatriation restrictions, withholding and other taxes, some of which may be confiscatory, inflation, deflation, currency devaluation and adverse government regulations of industries or markets. As a result of these risks, the prices of emerging market securities tend to be more volatile than the securities of issuers located in developed markets.
Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Investment Style Risk.  Different investment styles such as growth or value tend to shift in and out of favor, depending on market and economic conditions as well as investor sentiment. The Portfolio may outperform or underperform other funds that employ a different investment style.
Asset Allocation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Asset Allocation Risk.  The Portfolio’s ability to achieve its investment objective depends upon the Subadviser’s analysis of various factors and the mix of asset classes that results from such analysis, which may prove incorrect. The particular asset allocation selected for the Portfolio may not perform as well as other asset allocations that could have been selected for the Portfolio. The Portfolio may experience losses or poor relative performance if the Subadviser allocates a significant portion of the Portfolio’s assets to an asset class that does not perform as the Subadviser anticipated, including relative to other asset classes or subsets of asset classes. The Portfolio may underperform funds that allocate their assets differently than the Portfolio.
High Yield Debt Security Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] High Yield Debt Security Risk.  High yield debt securities, or “junk” bonds, may be more susceptible to market risk and credit and counterparty risk than investment grade debt securities because issuers of high yield debt securities are less secure financially and their securities are more sensitive to downturns in the economy. In addition, the secondary market for high yield debt securities may not be as liquid as that for higher rated debt securities. High-yield debt securities range from those for which the prospect for repayment of principal and interest is predominantly speculative to those which are currently in default on principal or interest payments or whose issuers are in bankruptcy.
Real Estate Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Real Estate Investment Risk.  Investments in real estate investment trusts and other real estate related securities may be adversely impacted by the performance of the real estate market generally or that of a particular sub-sector or geographic region.
Mortgage Backed and Asset Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Mortgage-Backed and Asset-Backed Securities Risk.  The value of investments in mortgage-backed and asset-backed securities is subject to interest rate risk and credit and counterparty risk. These securities are also subject to the risk that issuers will prepay the principal more quickly or more slowly than expected, which could cause the Portfolio to invest the proceeds in less attractive investments or increase the volatility of their prices. To the extent mortgage-backed and asset-backed securities held by the Portfolio are backed by lower rated securities, such as sub-prime obligations, or are subordinated to other interests in the same mortgage or asset pool, the likelihood of the Portfolio receiving payments of principal or interest may be substantially limited.
Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Interest Rate Risk.  The value of the Portfolio’s investments in fixed income securities may decline when prevailing interest rates rise or increase when interest rates fall. The longer a security’s maturity or duration, the greater its value will change in response to changes in interest rates. The interest earned on the Portfolio’s investments in fixed income securities may decline when prevailing interest rates fall. During periods of very low or negative interest rates, the Portfolio may be unable to maintain positive returns or pay dividends to Portfolio shareholders. Additionally, under certain market conditions in which interest rates are low or negative, the Portfolio may have a very low, or even negative yield. A low or negative yield would cause the Portfolio to lose money and the net asset value of the Portfolio’s shares to decline in certain conditions and over certain time periods. Changes in prevailing interest rates, particularly sudden changes, may also increase the level of volatility in fixed income and other markets, increase redemptions in the Portfolio’s shares and reduce the liquidity of the Portfolio’s debt securities and other income-producing holdings. Changes in interest rate levels are caused by a variety of factors, such as central bank monetary policies, inflation rates, and general economic and market conditions.
Credit and Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Credit and Counterparty Risk.  The value of the Portfolio’s investments may be adversely affected if a security’s credit rating is downgraded or an issuer of an investment held by the Portfolio fails to pay an obligation on a timely basis, otherwise defaults or is perceived by other investors to be less creditworthy. If a counterparty to a derivatives or other transaction with the Portfolio files for bankruptcy, becomes insolvent, or otherwise becomes unable or unwilling to honor its obligation to the Portfolio, the Portfolio may experience significant losses or delays in realizing income on or recovering collateral and may lose all or a part of the income from the transaction.
Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Derivatives Risk.  The Portfolio may invest in derivatives to obtain investment exposure, enhance return or “hedge” or protect its assets from an unfavorable shift in the value or rate of a reference instrument or asset. Derivatives can be highly volatile and can significantly increase the Portfolio’s exposure to market risk, credit and counterparty risk and other risks. Derivatives may be illiquid and difficult to value and can involve risks in addition to, and potentially greater than, the risks of the underlying reference instrument. Because of their complex nature, some derivatives may not perform as intended. As a result, the Portfolio may not realize the anticipated benefits from a derivative it holds or it may realize losses. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Derivative transactions may create investment leverage, which increases the Portfolio’s volatility and may require the Portfolio to liquidate portfolio securities when it is not advantageous to do so. Government regulation of derivative instruments may limit or prevent the Portfolio from using such instruments as part of its investment strategies, which could adversely affect the Portfolio.
Convertible Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Convertible Securities Risk.  Investments in convertible securities are subject to market risk, credit and counterparty risk, interest rate risk and other risks associated with investments in equity and fixed income securities, depending on the price of the underlying security and the conversion price. In addition, a convertible security may be bought back by the issuer, or the Portfolio may be forced to convert a convertible security, at a time and a price that is disadvantageous to the Portfolio.
Forward and Futures Contract Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Forward and Futures Contract Risk.  The successful use of forward and futures contracts will depend upon the Subadviser’s skill and experience with respect to such instruments and are subject to special risk considerations. The primary risks associated with the use of forward and futures contracts include (i) the imperfect correlation between the change in market value of the instruments held by the Portfolio and the price of the forward or futures contract; (ii) possible lack of a liquid market for a forward or futures contract and the resulting inability to close a forward or futures contract when desired; (iii) losses caused by unanticipated market movements, which are potentially unlimited; (iv) the Subadviser’s inability to predict correctly the direction of securities prices, interest rates, currency exchange rates and other economic factors; (v) the possibility that the counterparty will default in the performance of its obligations; (vi) if the Portfolio has insufficient cash, it may have to sell securities to meet daily variation margin requirements, and the Portfolio may have to sell securities at a time when it is disadvantageous to do so; (vii) the possibility that the Portfolio may be delayed or prevented from recovering margin or other amounts deposited with a futures commission merchant or clearinghouse; (viii) the possibility that position or trading limits will preclude the Subadviser from taking positions in certain futures contracts on behalf of the Portfolio; and (ix) the risks typically associated with foreign investments to the extent the Portfolio invests in derivatives traded on markets outside the United States.
Rule 144A and Other Exempted Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Rule 144A and Other Exempted Securities Risk.  In the U.S. market, private placements may typically be sold only to qualified institutional buyers, or qualified purchasers, as applicable. If an insufficient number of eligible buyers is interested in purchasing privately placed and other securities or instruments exempt from Securities and Exchange Commission registration (collectively “private placements”) at a particular time, this could adversely affect the marketability of such investments and the Portfolio might be unable to dispose of them promptly or at reasonable prices, subjecting the Portfolio to liquidity risk. Even the Portfolio’s holdings of liquid private placements may increase the level of Portfolio illiquidity if eligible buyers are unable or unwilling to purchase them at a particular time. The information that issuers of Rule 144A eligible securities are required to disclose to potential investors is much less extensive than that required of public companies and is not publicly available, and issuers of Rule 144A eligible securities can require recipients of the offering information (such as the Portfolio) to agree contractually to keep the information confidential, which could also adversely affect the Portfolio’s ability to dispose of the security.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money by investing in the Portfolio.
Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Portfolio through a Contract is not a deposit or obligation of, or guaranteed by, any bank, and is not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. Government.