Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BMO FUNDS, INC.
Prospectus Date	rr_ProspectusDate	Dec. 29, 2014
BMO Micro-Cap Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	BMO Micro-Cap Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	To provide capital appreciation.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
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 Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of certain BMO Funds. More information about these and other discounts is available from your financial professional and under “How to Buy Shares – Sales Charge” on page 113 of this Prospectus and under “How to Buy Shares – Waivers and Reductions of Sales Charges – Class A Shares” beginning on page 114 of this Prospectus and “How to Buy Shares” beginning on page B-43 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
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)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	December 31, 2015
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund incurs 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 and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal period ended August 31, 2014, the Fund’s portfolio turnover rate (not annualized) was 70% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	70.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	The Maximum Deferred Sales Charge on Class A shares is applied only to purchases of $1,000,000 or more that are redeemed within 18 months of purchase.
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of certain BMO Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	50,000
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	“Other Expenses” for the Class A shares are based on estimated amounts for the current fiscal year.
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Total Annual Fund Operating Expenses shown will not correlate to the Fund’s ratio of expenses to average net assets appearing in the Financial Highlights tables, which do not include Acquired Fund Fees and Expenses.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem 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 are as shown in the table and remain the same. The costs in the one-year example and for the first year of the three-, five-, and ten-year examples reflect the Adviser’s agreement to waive fees and reimburse expenses through December 31, 2015. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests at least 80% of its assets in a broadly diversified portfolio of common stocks of U.S. companies similar in size, at the time of purchase, to those within the Russell Microcap® Index. The largest company by market capitalization in the Russell Microcap® Index was approximately $2.8 billion as of October 31, 2014 and the median market capitalization of companies in the Index as of the same period was $211 million. The Adviser uses a disciplined investment process that identifies companies that it believes have good value relative to their assets, sustainable cash flow, acceptable levels of debt, and potential for improving their business fundamentals. In addition, these companies may have under-appreciated assets, or be involved in company turnarounds or corporate restructurings.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The Fund cannot assure that it will achieve its investment objective. An investment in the Fund is not a deposit of BMO Harris Bank N.A., or any of its affiliates, and is not insured or guaranteed by the FDIC or any other government agency. The net asset value of the Fund will vary and you could lose money by investing in the Fund. In addition, the Fund is subject to the following risks. Stock Market Risks. The Fund is subject to fluctuations in the stock market, which has periods of increasing and decreasing values. Stocks are more volatile than debt securities. The value of equity securities purchased by the Fund may decline if the financial condition of the companies in which the Fund invests declines or if overall market and economic conditions deteriorate. If the value of the Fund’s investments goes down, you may lose money. Sector Risks. Companies with similar characteristics, such as those within the same industry, may be grouped together in broad categories called sectors. To the extent the Fund invests its assets in a particular sector, the Fund’s performance may be more susceptible to any economic, business, or other developments that generally affect that sector. Micro-Cap Company Risks. Generally, micro-cap companies have fewer shares traded daily, less liquid stock, and more volatile prices than larger capitalization companies. Micro-cap companies are more vulnerable to adverse business or economic developments than companies with larger capitalizations. If the Fund wants to sell a large quantity of a micro-cap company’s stock, it may have to sell at a lower price than the Adviser might prefer, or it may have to sell in smaller than desired quantities over a period of time. Micro-cap companies also tend to have unproven track records, limited management experience, a limited product or service base, less publicly available information, and limited access to capital. These factors also increase risks and make these companies more likely to fail than companies with larger market capitalizations. Management Risks. The Adviser’s judgments about the attractiveness, value, and potential appreciation of the Fund’s investments may prove to be incorrect. Accordingly, no guarantee exists that the investment techniques used by the Fund’s managers will produce the desired results. Corporate Restructuring Risks. Securities of companies that are involved in company turnarounds or corporate restructurings may present special risk because of the high degree of uncertainty that can be associated with such events. It is possible that the market price of securities of companies involved in company turnarounds or corporate restructurings may be subject to significant and unpredictable fluctuations.
Risk Lose Money [Text]	rr_RiskLoseMoney	The net asset value of the Fund will vary and you could lose money by investing in the Fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the Fund is not a deposit of BMO Harris Bank N.A., or any of its affiliates, and is not insured or guaranteed by the FDIC or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Fund Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	Performance information is not included because the Fund does not have one full calendar year of performance as of the date of this Prospectus.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Performance information is not included because the Fund does not have one full calendar year of performance as of the date of this Prospectus.
BMO Micro-Cap Fund | Class Y
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of shares redeemed within 18 months of purchase)	rr_MaximumDeferredSalesChargeOverOther	none	[1]
Redemption Fee	rr_RedemptionFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.90%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	5.71%	[2]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	6.62%
Fee Waiver and Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(5.26%)	[4]
Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement	rr_NetExpensesOverAssets	1.36%	[4]
1 Year	rr_ExpenseExampleYear01	138
3 Years	rr_ExpenseExampleYear03	1,489
5 Years	rr_ExpenseExampleYear05	2,795
10 Years	rr_ExpenseExampleYear10	5,881
BMO Micro-Cap Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of shares redeemed within 18 months of purchase)	rr_MaximumDeferredSalesChargeOverOther	none	[1]
Redemption Fee	rr_RedemptionFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.90%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	5.46%	[2]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	6.37%
Fee Waiver and Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(5.26%)	[4]
Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement	rr_NetExpensesOverAssets	1.11%	[4]
1 Year	rr_ExpenseExampleYear01	113
3 Years	rr_ExpenseExampleYear03	1,419
5 Years	rr_ExpenseExampleYear05	2,689
10 Years	rr_ExpenseExampleYear10	5,714
BMO Micro-Cap Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	5.00%
Maximum Deferred Sales Charge (Load) (as a percentage of shares redeemed within 18 months of purchase)	rr_MaximumDeferredSalesChargeOverOther	1.00%	[1]
Redemption Fee	rr_RedemptionFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.90%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	5.46%	[2]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	6.62%
Fee Waiver and Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(5.26%)	[4]
Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement	rr_NetExpensesOverAssets	1.36%	[4]
1 Year	rr_ExpenseExampleYear01	632
3 Years	rr_ExpenseExampleYear03	1,914
5 Years	rr_ExpenseExampleYear05	3,155
10 Years	rr_ExpenseExampleYear10	6,087

[1] The Maximum Deferred Sales Charge on Class A shares is applied only to purchases of $1,000,000 or more that are redeemed within 18 months of purchase.

[2] "Other Expenses" for the Class A shares are based on estimated amounts for the current fiscal year.

[3] Acquired Fund Fees and Expenses represent the pro rata expense indirectly incurred by the Fund as a result of its investment in other investment companies. Total Annual Fund Operating Expenses shown will not correlate to the Fund's ratio of expenses to average net assets appearing in the Financial Highlights tables, which do not include Acquired Fund Fees and Expenses.

[4] BMO Asset Management Corp. (Adviser) has agreed to waive or reduce its investment advisory fee and reimburse expenses to the extent necessary to prevent class total annual operating expenses (excluding interest, taxes, brokerage commissions, other investment-related costs, and extraordinary expenses, such as litigation and other expenses not incurred in the ordinary course of the Fund's business, and Acquired Fund Fees and Expenses) from exceeding 1.35% for Class Y, 1.10% for Class I, and 1.35% for Class A through December 31, 2015. This expense limitation agreement may not be terminated prior to December 31, 2015 without the consent of the Fund's Board of Directors, unless terminated due to the termination of the investment advisory agreement.