This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and Example below. Additional fees and expenses will be applied at the variable contract level. Those fees and expenses are described in your variable contract prospectus. If the information below were to reflect the deduction of variable contract charges, fees and expenses would be higher.

Operating Expenses Caption [Text]

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

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 51% of the average value of its portfolio.

Portfolio Turnover, Rate

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51.00%

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example does not reflect expenses and charges which are, or may be, imposed under your variable contract. If the examples were to reflect the deduction of such charges, the costs shown would be greater. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem or hold 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 Fund’s operating expenses remain the same. Although your actual costs and returns might be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Principal Investment Strategy

Strategy Narrative [Text Block]

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Under normal market conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of medium capitalization companies. For purposes of the Fund’s investments, equity securities include common stock, preferred stock, and equity-equivalent securities, such as convertible securities, stock futures contracts or stock index futures contracts. The Sub‑Adviser considers medium size companies whose market capitalization at the time of purchase is within the capitalization range of the Russell 3000^® Index, excluding the largest 100 such companies, for inclusion in the Fund’s portfolio. As of March 31, 2022, and as provided by the Sub‑Adviser, this capitalization range was between $12.14 million and $82.5 billion. The Sub‑Adviser intends to manage the Fund so that its weighted capitalization falls within the capitalization range of the members of the Russell Midcap^® Index. As of March 31, 2022, and as provided by the Sub‑Adviser, this capitalization range was between $136.27 million and $61.3 billion. In selecting stocks for the Fund, the Sub‑Adviser looks for companies whose stock price may not reflect the company’s value. The Sub‑Adviser attempts to purchase the stocks of these undervalued companies and hold

each stock until the price has increased to, or is higher than, a level the Sub‑Adviser believes more accurately reflects the fair value of the company. The Fund may invest a portion of its assets in foreign securities when these securities meet the Sub‑Adviser’s standards of selection. The Sub‑Adviser may sell stocks from the Fund’s portfolio if it believes a stock no longer meets its valuation criteria, a stock’s risk parameters outweigh its return opportunity, more attractive alternatives are identified or specific events alter a stock’s prospects. The Fund may engage in active and frequent trading of portfolio securities in the pursuit of its investment objective.

While the Fund’s sector and industry exposure is expected to vary over time, as of February 28, 2022, the Fund had significant exposure to the Financials Sector, Health Care Sector, and Industrials Sector, as each sector is defined by the Global Industry Classification Standard.

Risk [Heading]

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Principal Risks of Investing

Risk Narrative [Text Block]

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As with all mutual funds, an investor is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

Mid‑Cap Securities Risk. The possibility that the return on the Fund’s investments in mid‑cap companies may be less than the return on investments in stocks of larger or smaller companies or the stock market as a whole. Mid‑cap companies may be more vulnerable to market volatility and adverse business or economic events than larger, more established companies. The securities of mid‑cap companies are more likely to trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.

“Value” Investing Risk. The possibility that the Fund’s investments in securities believed by the Sub‑Adviser to be undervalued may not realize their perceived value for extended periods of time or may never realize their perceived value. The securities in which the Fund invests may respond differently to market and other developments than other types of securities, and may underperform growth stocks and/or the market as a whole, particularly if the Fund’s investment style shifts out of favor.

Equity Securities Risk. In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions.

Market Risk. The possibility that the values of, and/or the income generated by, securities held by the Fund may decline, sometimes unpredictably, due to general market conditions or other factors, including those directly involving the issuers of such securities. Security markets are volatile and may decline significantly in response to adverse issuer, regulatory, political, or economic developments. Different sectors of the market and different security types may react differently to such developments.

Foreign Investment Risk. The possibility that the Fund’s investments in foreign securities may be adversely affected by political, social, and economic conditions affecting foreign issuers or decreases in foreign currency values relative to the U.S. dollar. Investments in foreign markets may be subject to greater market volatility, decreased market liquidity, and higher transaction and custody costs. Foreign issuers also may be subject to less government and exchange regulation and there may be less reliable financial information available for such issuers and their securities.

Portfolio Turnover Risk. The possibility that the Fund may frequently buy and sell portfolio securities, which may increase transaction costs to the Fund and cause the Fund’s performance to be less than you expect.

Liquidity Risk. The possibility that the market for certain of the Fund’s investments may become illiquid under adverse or volatile market or economic conditions, making those investments difficult to sell at an advantageous price, particularly in times of market turmoil. The market price of certain investments may fall dramatically if there is no liquid trading market for the investments. Illiquid securities may also be more difficult to value. If the Fund is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.

Management Risk. The possibility that the investment decisions, techniques, analyses or models implemented by the Fund’s Sub‑Adviser in seeking to achieve the Fund’s investment objective may not produce the returns expected, may cause the Fund’s shares to lose value or may cause the Fund to underperform relevant benchmarks or other funds with similar investment objectives.

Sector Risk. The possibility that the Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector, including adverse market conditions, legislative or regulatory changes, and/or increased competition affecting that sector, than funds that invest more broadly. While the Fund’s sector and industry exposure is expected to vary over time, as of February 28, 2022, the Fund had significant exposure to the Financials Sector, Health Care Sector, and Industrials Sector. In addition to these general risks, the sectors specified are also subject to the risks described below.

Financials Sector Risk. The Financials Sector includes companies involved in banking, thrifts and mortgage finance, specialized finance, consumer finance, asset management and custody banks, investment banking and brokerage and insurance. It also includes the Financial Exchanges & Data and Mortgage Real Estate Investment Trusts (“REITs”) sub‑industries. Certain financial sector companies serve as counterparties with which the Fund may enter into derivatives agreements or other similar contractual arrangements. Companies operating in the Financials Sector are subject to extensive government regulation, which may limit the financial commitments they can make and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition.

Health Care Sector Risk. The Health Care Sector includes health care providers and services, companies that manufacture and distribute health care equipment and supplies, and health care technology companies. It also includes companies involved in the research, development, production and marketing of pharmaceuticals and biotechnology products. The prices of the securities of companies operating in this sector are closely tied to government regulation and approval of their products and services, which can have a significant effect on the price and availability of those products and services. This sector also can be significantly affected by, among other things, lapsing patent protection, technological developments that make drugs obsolete, and price controls.

Industrials Sector Risk. The Industrials Sector includes manufacturers and distributors of capital goods such as aerospace and defense, building projects, electrical equipment and machinery and companies that offer construction and engineering services. It also includes providers of commercial and professional services including printing, environmental and facilities services, office services and supplies, security and alarm services, human resource and employment services, research and consulting services. It also includes companies that provide transportation services. The prices of the securities of companies operating in the Industrials Sector may fluctuate due to the level and volatility of commodity prices, the exchange value of the dollar, import controls, worldwide competition, liability for environmental damage, depletion of resources, and mandated expenditures for safety and pollution control devices.

IPOs Risk. The possibility that the Fund’s performance may be affected by the purchase of securities issued in initial public offerings (IPOs) that have little to no trading history, limited issuer information, increased volatility and may not be available to the extent desired. The prices of securities bought in IPOs may rise and fall rapidly, often because of investor perceptions rather than economic reasons.

An investment in the Fund may be appropriate for investors who are willing to accept the risks and uncertainties of investing in mid‑cap stocks in the hope of achieving above-average growth of capital.

Risk Lose Money [Text]

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As with all mutual funds, an investor is subject to the risk that his or her investment could lose money.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below show the performance of the Fund both year‑by‑year and as an average over different periods of time. Performance prior to May 1, 2013 reflects the Fund’s investment performance when managed by a previous sub‑adviser pursuant to a substantially similar principal investment strategy. Since May 1, 2013, American Century Investment Management, Inc. has been responsible for the Fund’s day‑to‑day portfolio management. Therefore, the performance and average annual total returns shown for periods prior to May 1, 2013 may have differed had American Century Investment Management, Inc. been responsible for the day‑to‑day portfolio management during those periods. The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index. Past performance does not necessarily indicate how the Fund will perform in the future. This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart and table demonstrate the variability of performance over time and provide an indication of the risks and volatility of an investment in the Fund by showing how the Fund’s average annual total returns for various periods compare with those of a broad-based securities market index.

Performance Past Does Not Indicate Future [Text]

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Past performance does not necessarily indicate how the Fund will perform in the future.

Bar Chart Does Not Reflect Sales Loads [Text]

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This performance information does not include the impact of any charges deducted under your variable contract. If it did, returns would be lower.

Bar Chart Closing [Text Block]

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