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Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Alger Capital Appreciation Portfolio
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

Alger Capital Appreciation Portfolio seeks long-term capital appreciation.

Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. The table does not reflect fees, expenses, or charges that may be imposed by the separate accounts of life insurance companies or qualified pension or retirement plans. If it did, the fees would be higher.

Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Shareholder Fees (fees paid directly from your investment) rr_ShareholderFeeOther none
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Advisory Fees rr_ManagementFeesOverAssets 0.81% [1]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.15%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.96%
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's turnover rate was 139.19% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 139.19%
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following example, which reflects the shareholder fees and operating expenses listed above, is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in Class I-2 shares of the Portfolio for the time periods indicated, that your investment has a 5% return each year and that the Portfolio's operating expenses remain the same. The example does not reflect fees, expenses, or charges that may be imposed by the separate accounts of life insurance companies or qualified pension or retirement plans. If it did, the expenses would be higher.

Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on these assumptions you would pay the following expenses whether or not you redeemed your shares at the end of each period:
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 98
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 306
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 531
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,178
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGY
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Fred Alger Management, Inc. believes companies undergoing Positive Dynamic Change offer the best investment opportunities. Positive Dynamic Change refers to companies realizing High Unit Volume Growth or companies undergoing Positive Lifecycle Change. High Unit Volume Growth companies are traditional growth companies experiencing, for example, significantly growing demand or market dominance. Positive Lifecycle Change companies are, for example, companies benefitting from regulatory change, a new product introduction or management change.


Under normal market circumstances, the Portfolio invests at least 85% of its net assets, plus any borrowings for investment purposes, in equity securities of companies of any market capitalization that Fred Alger Management, Inc. believes demonstrate promising growth potential.


The Portfolio can leverage, that is, borrow money to buy additional securities. By borrowing money, the Portfolio has the potential to increase its returns if the increase in the value of the securities purchased exceeds the cost of borrowing, including interest paid on the money borrowed.


The Portfolio can also invest in derivative instruments. The Portfolio currently expects that its primary use of derivatives will involve entering into forward currency contracts to hedge the Portfolio's foreign currency exposure when it holds, or proposes to hold, non-U.S. dollar denominated securities.

Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

As with any fund that invests in stocks, your investment will fluctuate in value, and the loss of your investment is a risk of investing. The Portfolio's price per share will fluctuate due to changes in the market prices of its investments. Also, the Portfolio's investments may not grow as fast as the rate of inflation and stocks tend to be more volatile than some other investments you could make, such as bonds.


Prices of growth stocks tend to be higher in relation to their companies' earnings and may be more sensitive to market, political and economic developments than other stocks, making their prices more volatile. An investment in the Portfolio may be better suited to investors who seek long-term capital growth and can tolerate fluctuations in their investment's value.


A small investment in derivatives could have a potentially large impact on the Portfolio's performance. Forward currency contracts are subject to currency exchange rate risks and the risk of non-performance by the contract counterparty.


The following risks may also apply:


•  investing in companies of all capitalizations involves the risk that smaller issuers in which the Portfolio invests may have limited product lines or financial resources, or lack management depth.


•  it may be difficult or impossible to liquidate a security position at a time and price acceptable to the Portfolio because of the potentially less frequent trading of stocks of smaller market capitalization.


•  the cost of borrowing money to leverage may exceed the returns for the securities purchased or the securities purchased may actually go down in value; thus, the Portfolio's net asset value can decrease more quickly than if the Portfolio had not borrowed.


An investment in the Portfolio is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Lose Money [Text] rr_RiskLoseMoney As with any fund that invests in stocks, your investment will fluctuate in value, and the loss of your investment is a risk of investing.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Portfolio is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following bar chart and the table beneath it provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio's performance from year to year and by showing how the Portfolio's average annual returns for the indicated periods compare with those of an appropriate benchmark of market performance. The Russell 1000 Growth Index is an index of common stocks designed to track performance of large capitalization companies with greater than average growth orientation. The performance numbers do not reflect fees, expenses, or charges that may be imposed by the separate accounts of life insurance companies or qualified pension or retirement plans. If they did, the performance numbers would be lower. Remember that the Portfolio's past performance is not necessarily an indication of how it will perform in the future. Updated performance information is available on the Portfolio's website www.alger.com.

Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and the table beneath it provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio's performance from year to year and by showing how the Portfolio's average annual returns for the indicated periods compare with those of an appropriate benchmark of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.alger.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Remember that the Portfolio's past performance is not necessarily an indication of how it will perform in the future.
Bar Chart [Heading] rr_BarChartHeading ANNUAL TOTAL RETURN FOR CLASS I-2 SHARES as of December 31 (%)
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The performance numbers do not reflect fees, expenses, or charges that may be imposed by the separate accounts of life insurance companies or qualified pension or retirement plans.
Annual Return 2003 rr_AnnualReturn2003 34.72%
Annual Return 2004 rr_AnnualReturn2004 8.19%
Annual Return 2005 rr_AnnualReturn2005 14.45%
Annual Return 2006 rr_AnnualReturn2006 19.26%
Annual Return 2007 rr_AnnualReturn2007 33.53%
Annual Return 2008 rr_AnnualReturn2008 (45.13%)
Annual Return 2009 rr_AnnualReturn2009 51.10%
Annual Return 2010 rr_AnnualReturn2010 14.03%
Annual Return 2011 rr_AnnualReturn2011 (0.30%)
Annual Return 2012 rr_AnnualReturn2012 18.30%
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter


Q2 2009   20.74%


Worst Quarter


Q4 2008   -22.55%

Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 20.74%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (22.55%)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Caption rr_AverageAnnualReturnCaption AVERAGE ANNUAL TOTAL RETURN AS OF DECEMBER 31, 2012
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 18.30%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.20%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.47%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 12.39%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Jan. 25, 1995
Russell 1000 Growth Index (reflects no deduction for fees, expenses or taxes)
  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 15.26%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 3.12%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 7.52%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 7.58%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Jan. 25, 1995
[1] The Portfolio and Fred Alger Management, Inc. have adopted breakpoints for Alger Capital Appreciation Portfolio. The management fee for assets in excess of $2 billion is .65%, with an additional breakpoint of .60% for assets in excess of $4 billion.