Average Annual Total Returns - Class Z Shares - Alger Small Cap Focus Fund - AC	Class Z Inception Date	Class Z Return Before Taxes 1 Year	Class Z Return Before Taxes 5 Years	Class Z Return Before Taxes 10 Years	Class Z Return After Taxes on Distributions 1 Year	Class Z Return After Taxes on Distributions 5 Years	Class Z Return After Taxes on Distributions 10 Years	Class Z Return After Taxes on Distributions and Sale of Fund Shares 1 Year	Class Z Return After Taxes on Distributions and Sale of Fund Shares 5 Years	Class Z Return After Taxes on Distributions and Sale of Fund Shares 10 Years	Russell 2000 Growth Index (reflects no deductions for fees, expenses or taxes) 1 Year	Russell 2000 Growth Index (reflects no deductions for fees, expenses or taxes) 5 Years	Russell 2000 Growth Index (reflects no deductions for fees, expenses or taxes) 10 Years
Total	Dec. 29, 2010	53.78%	25.19%	17.09%	53.78%	24.88%	15.84%	31.84%	20.73%	13.88%	34.63%	16.36%	13.48%