Alger Mid Cap Focus Fund Expense Example - Class I Shares [Member] - Alger Mid Cap Focus Fund - Class I	Oct. 31, 2025 USD ($)
Prospectus [Line Items]
Expense Example, with Redemption, 1 Year	$ 117
Expense Example, with Redemption, 3 Years	365
Expense Example, with Redemption, 5 Years	633
Expense Example, with Redemption, 10 Years	$ 1,398

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