Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

BMO FUNDS, INC.

Prospectus Date

rr_ProspectusDate

Dec. 29, 2014

BMO Mortgage Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

BMO Mortgage Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

To provide current income.

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 $100,000 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 110 of this Prospectus and under “How to Buy Shares – Waivers and Reductions of Sales Charges – Class A Shares” beginning on page 111 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 year, the Fund’s portfolio turnover rate was 129% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

129.00%

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 $100,000 in Class A shares of certain BMO Funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

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 Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

Management Fees and Other Expenses have been restated to reflect current fees, effective June 1, 2015.

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 mortgage-related securities issued or sponsored by the U.S. government or its agencies and instrumentalities. The securities in which the Fund invests generally will have a minimum rating no lower than the lowest investment grade category (i.e., rated BBB or Baa, or higher, or unrated and considered by the Adviser to be comparable in quality) at the time of purchase.

The Fund invests in the securities of U.S. government-sponsored entities that are not backed by the full faith and credit of the U.S. government, but are supported through federal loans or other benefits, including the Federal Home Loan Banks (FHLBs), Federal National Mortgage Association (Fannie Mae), and Federal Home Loan Mortgage Corporation (Freddie Mac). The Fund also may invest in the securities of U.S. government-sponsored entities that are supported by the full faith and credit of the U.S. government, such as the Government National Mortgage Association (Ginnie Mae). Finally, the Fund may invest in the securities of governmental entities that have no explicit financial support from the U.S. government, but are regarded as having implied support because the U.S. government sponsors their activities, including the Farm Credit Administration and the Financing Corporation. The Fund also may invest in non-agency asset-backed and mortgage-backed securities.

The Adviser considers macroeconomic conditions and uses credit and market analysis in developing the overall portfolio strategy. Current and historical interest rate relationships are used to evaluate market sectors and individual securities. The Fund normally maintains an average dollar-weighted effective maturity of four to twelve years. Effective maturity takes into account the possibility that a bond may have prepayments or may be called by the issuer before its stated maturity date.

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.

Interest Rate Risks. Prices of fixed income securities rise and fall in response to changes in the interest rate paid by similar securities. Generally, when interest rates rise, prices of fixed income securities fall. Interest rate changes have a greater effect on the price of fixed income securities with longer maturities.

Credit Risks. Credit risk is the possibility that an issuer or counterparty will default on a security or repurchase agreement by failing to pay interest or principal when due. If an issuer defaults, the Fund may lose money. Lower credit ratings correspond to higher credit risk. Bonds rated lower than BBB or Baa have speculative characteristics.

Call Risks. If the securities in which the Fund invests are redeemed by the issuer before maturity (or “called”), the Fund may have to reinvest the proceeds in securities that pay a lower interest rate, which may decrease the Fund’s yield. This will most likely happen when interest rates are declining.

Liquidity Risks. Liquidity risk refers to the possibility that the Fund may not be able to sell or buy a security or close out an investment contract at a favorable price or time. Consequently, the Fund may have to accept a lower price to sell a security, sell other securities to raise cash, or give up an investment opportunity, any of which could have a negative effect on the Fund’s performance. Infrequent trading of securities also may lead to an increase in their price volatility.

Asset-Backed/Mortgage-Backed Securities Risks. Asset-backed and mortgage-backed securities are subject to risks of prepayment. The Fund’s yield will be reduced if cash from prepaid securities is reinvested in securities with lower interest rates. The risk of prepayment also may decrease the value of mortgage-backed securities. Asset-backed securities may have a higher level of default and recovery risk than mortgage-backed securities. Both of these types of securities may decline in value because of mortgage foreclosures or defaults on the underlying obligations. Credit risk is greater for mortgage-backed securities that are subordinate to another security.

Government Obligations Risks. No assurance can be given that the U.S. government will provide financial support to U.S. government-sponsored agencies or instrumentalities where it is not obligated to do so by law. As a result, there is risk that these entities will default on a financial obligation.

Income Risks. The Fund’s income could decline due to falling market interest rates. In a falling interest rate environment, the Fund may be required to invest its assets in lower-yielding securities.

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.

Portfolio Turnover Risks. A high portfolio rate (100% or more) may result in the realization and distribution to shareholders of a greater amount of capital gains than if the Fund had a low portfolio turnover rate. Therefore, you may have higher tax liability. High portfolio turnover also may result in higher transaction costs, which may negatively affect Fund performance.

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

The bar chart and table show the historical performance of the Fund’s shares and provide some indication of the risks of investing in the Fund. The bar chart shows how the Fund’s total returns before taxes have varied from year to year, while the table compares the Fund’s average annual total returns to the returns of a broad measure of market performance and an index of funds with similar investment objectives. Please keep in mind that past performance, before and after taxes, does not represent how the Fund will perform in the future. Investors may obtain updated performance information for the Fund at www.bmofunds.com.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table show the historical performance of the Fund’s shares and provide some indication of the risks of investing in the Fund. The bar chart shows how the Fund’s total returns before taxes have varied from year to year, while the table compares the Fund’s average annual total returns to the returns of a broad measure of market performance and an index of funds with similar investment objectives.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

Because Class A shares have not been offered for a full calendar year, the information provided represents returns of Class Y and Class I shares.

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

The Barclays U.S. MBS Index (BMI) tracks agency mortgage-backed pass-through securities guaranteed by Ginnie Mae, Freddie Mac, and Fannie Mae.

The Lipper U.S. Mortgage Funds Index (LUSMI) tracks the total return performance of the 30 largest mutual funds included in this Lipper category.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.bmofunds.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Please keep in mind that past performance, before and after taxes, does not represent how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class Y—Annual Total Returns (calendar years 2004-2013)

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The bar chart does not reflect the payment of any sales charges. If these charges had been reflected, the returns shown would have been lower.

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

* The bar chart does not reflect the payment of any sales charges. If these charges had been reflected, the returns shown would have been lower.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The return for the Class Y shares of the Fund from January 1, 2014 through September 30, 2014 was 3.93%.

During the periods shown in the bar chart for the Fund:

	Quarter Ended		Returns
Best quarter		9/30/2009		5.39	%
Worst quarter		6/30/2013		(2.39)	%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns through 12/31/13

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the highest historical individual marginal federal income tax rates and do not reflect the effect of any applicable state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors holding shares through tax-deferred programs, such as IRAs or 401(k) plans.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown only for Class Y, and after-tax returns for Class I and Class A will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

The Return After Taxes on Distributions and Sale of Fund Shares may be higher than other return figures when a capital loss is realized on the sale of Fund shares which provides an assumed tax benefit to the shareholder that increases the after tax return.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using the highest historical individual marginal federal income tax rates and do not reflect the effect of any applicable state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors holding shares through tax-deferred programs, such as IRAs or 401(k) plans. After-tax returns are shown only for Class Y, and after-tax returns for Class I and Class A will vary.

The Return After Taxes on Distributions and Sale of Fund Shares may be higher than other return figures when a capital loss is realized on the sale of Fund shares which provides an assumed tax benefit to the shareholder that increases the after tax return.

The Barclays U.S. MBS Index (BMI) tracks agency mortgage-backed pass-through securities guaranteed by Ginnie Mae, Freddie Mac, and Fannie Mae.

The Lipper U.S. Mortgage Funds Index (LUSMI) tracks the total return performance of the 30 largest mutual funds included in this Lipper category.

BMO Mortgage Income 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

0.23%

^[2],[3]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.58%

^[3],[4]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.81%

Fee Waiver and Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[5]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

0.80%

^[5]

1 Year

rr_ExpenseExampleYear01

82

3 Years

rr_ExpenseExampleYear03

258

5 Years

rr_ExpenseExampleYear05

449

10 Years

rr_ExpenseExampleYear10

1,001

2004

rr_AnnualReturn2004

4.24%

2005

rr_AnnualReturn2005

2.33%

2006

rr_AnnualReturn2006

4.72%

2007

rr_AnnualReturn2007

5.85%

2008

rr_AnnualReturn2008

0.07%

2009

rr_AnnualReturn2009

12.71%

2010

rr_AnnualReturn2010

7.08%

2011

rr_AnnualReturn2011

5.20%

2012

rr_AnnualReturn2012

3.81%

2013

rr_AnnualReturn2013

(2.32%)

Year to Date Return, Label

rr_YearToDateReturnLabel

The return for the Class Y shares of the Fund from January 1, 2014 through September 30, 2014

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2014

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

3.93%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.39%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2013

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.39%)

1 Year

rr_AverageAnnualReturnYear01

(2.32%)

^[6]

5 Year

rr_AverageAnnualReturnYear05

5.18%

^[6]

10 Year

rr_AverageAnnualReturnYear10

4.30%

^[6]

Since Class I Inception

rr_AverageAnnualReturnSinceInception

^[6]

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 13, 1992

^[6]

BMO Mortgage Income 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

0.23%

^[2],[3]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.33%

^[3],[4]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.56%

Fee Waiver and Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[5]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

0.55%

^[5]

1 Year

rr_ExpenseExampleYear01

56

3 Years

rr_ExpenseExampleYear03

178

5 Years

rr_ExpenseExampleYear05

312

10 Years

rr_ExpenseExampleYear10

700

1 Year

rr_AverageAnnualReturnYear01

(2.19%)

^[6]

5 Year

rr_AverageAnnualReturnYear05

5.44%

^[6]

10 Year

rr_AverageAnnualReturnYear10

^[6]

Since Class I Inception

rr_AverageAnnualReturnSinceInception

4.90%

^[6]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2007

^[6]

BMO Mortgage Income Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.50%

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

0.23%

^[2],[3]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.33%

^[3],[4]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.81%

Fee Waiver and Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[5]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

0.80%

^[5]

1 Year

rr_ExpenseExampleYear01

429

3 Years

rr_ExpenseExampleYear03

599

5 Years

rr_ExpenseExampleYear05

783

10 Years

rr_ExpenseExampleYear10

1,316

BMO Mortgage Income Fund | Return After Taxes on Distributions | Class Y

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(3.31%)

^[6]

5 Year

rr_AverageAnnualReturnYear05

3.63%

^[6]

10 Year

rr_AverageAnnualReturnYear10

2.61%

^[6]

Since Class I Inception

rr_AverageAnnualReturnSinceInception

^[6]

BMO Mortgage Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class Y

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(1.31%)

^[6]

5 Year

rr_AverageAnnualReturnYear05

3.54%

^[6]

10 Year

rr_AverageAnnualReturnYear10

2.74%

^[6]

Since Class I Inception

rr_AverageAnnualReturnSinceInception

^[6]

BMO Mortgage Income Fund | BMI (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(1.41%)

^[6]

5 Year

rr_AverageAnnualReturnYear05

3.69%

^[6]

10 Year

rr_AverageAnnualReturnYear10

4.61%

^[6]

Since Class I Inception

rr_AverageAnnualReturnSinceInception

4.87%

^[6]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2007

^[6]

BMO Mortgage Income Fund | LUSMI (reflects deduction of fees and no deduction for sales charges or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(1.21%)

^[6]

5 Year

rr_AverageAnnualReturnYear05

4.92%

^[6]

10 Year

rr_AverageAnnualReturnYear10

4.20%

^[6]

Since Class I Inception

rr_AverageAnnualReturnSinceInception

4.62%

^[6]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2007

^[6]

[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] The management fee disclosed is a blended fee based on the Fund’s total assets as of August 31, 2014. Under the investment advisory agreement, the Fund pays a management fee of 0.25% on the Fund’s first $100,000,000 of average daily net assets.

[3] Management Fees and Other Expenses have been restated to reflect current fees, effective June 1, 2015.

[4] “Other Expenses” for the Class A shares are based on estimated amounts for the current fiscal year.

[5] 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 0.80% for Class Y, 0.55% for Class I, and 0.80% 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.

[6] Because Class A shares have not been offered for a full calendar year, the information provided represents returns of Class Y and Class I shares. Class A shares (without the reflection of the payment of sales charges) would have substantially similar annual returns because the shares are invested in the same portfolio of securities. The performance of Class A shares (without the reflection of the payment of sales charges) will be the same as the Class Y shares because the Class A and Class Y shares have the same Total Annual Fund Operating Expenses. However, Class A shares do charge a front-end sales charge, so the performance of Class A shares reflecting the payment of sales charges would be lower than Class Y shares.