Business combination contingent consideration arrangements of shares issued.

No definition available.

Name:	mitk_BusinessCombinationContingentConsiderationArrangementsOfSharesIssued
Namespace Prefix:	mitk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Common stock trading period.

+ References

No definition available.

+ Details

Name:	mitk_CommonStockTradingPeriod
Namespace Prefix:	mitk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	mitk_PreferredStockDividendNumberOfSharesIssuedPerCommonStock
Namespace Prefix:	mitk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	mitk_PreferredStockLiquidationPreferencePerRight
Namespace Prefix:	mitk_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	mitk_PreferredStockShareConversionRatio
Namespace Prefix:	mitk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	mitk_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRateFromMarketPriceOfferingDate
Namespace Prefix:	mitk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	mitk_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRateFromMarketPricePurchaseDate
Namespace Prefix:	mitk_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation, Employee Stock Purchase Plans, Share Outstanding

+ References

No definition available.

+ Details

Name:	mitk_ShareBasedCompensationEmployeeStockPurchasePlansShareOutstanding
Namespace Prefix:	mitk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The per share price that the individual must pay to acquire shares under the deferred compensation arrangement.

+ References

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_PreferredStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21488-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21564-112644

+ Details

Name:	us-gaap_PreferredStockRedemptionPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=mitk_IDCheckerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mitk_EarnoutSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=mitk_PerformanceOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TitleOfIndividualAxis=us-gaap_ChiefExecutiveOfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=mitk_A2012PlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=mitk_PriorPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=mitk_EmployeeStockPurchasePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=mitk_DirectorPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended	12 Months Ended
	Nov. 06, 2018 $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Sep. 30, 2015 shares	Sep. 30, 2016 shares	Oct. 23, 2018 $ / right $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares	Mar. 07, 2018 shares	Mar. 10, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense \| $		$ 25,500
Weighted average period for unrecognized compensation expense expected to be recognized (in years)		2 years 9 months 18 days
Purchase of common stock (in shares)		3,032,660					2,806,364
Recognized compensation expense \| $		$ 2,670	$ 1,889
Total intrinsic value of options exercised \| $		$ 800	400
Weighted average fair value of options granted (in dollars per share) \| $ / shares		$ 4.35
Aggregate intrinsic value of options outstanding \| $		$ 16,700					$ 8,700
Preferred stock, par value (in dollars per share) \| $ / shares		$ 0.001				$ 0.001	$ 0.001
IDchecker
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business combination, paid earnout shares issued (in shares)				137,306	81,182
Earnout shares \| IDchecker
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized compensation expense \| $			400
Common stock trading period (in days)		10 days
Series B Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of preferred share purchase right for each share of common stock (in shares)						1
Preferred stock, share conversion ratio						0.001
Preferred stock, purchase price per right (in dollars per right) \| $ / right						35.00
Preferred stock, redemption price per share (in dollars per share) \| $ / shares						$ 0.0001
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unrecognized compensation expense expected to be recognized (in years)		2 years 9 months 18 days
RSUs outstanding (in shares)		2,949,147					2,580,176
Recognized compensation expense \| $		$ 2,000	1,200
Unrecognized compensation expense related to nonvested awards \| $		$ 19,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unrecognized compensation expense expected to be recognized (in years)		3 years 4 months 24 days
Recognized compensation expense \| $		$ 200	300
Unrecognized compensation expense related to outstanding stock options \| $		2,900
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense \| $		$ 1,400
Weighted average period for unrecognized compensation expense expected to be recognized (in years)		1 year 8 months 12 days
Performance Options \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense \| $		$ 2,300
Weighted average period for unrecognized compensation expense expected to be recognized (in years)		2 years 9 months 18 days
Number of common stock reserved for future grants (in shares)	800,000
Recognized compensation expense \| $		$ 100
Exercise price per share (in dollars per share) \| $ / shares	$ 9.50
Vesting period of awards	3 years
2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)									9,500,000
Purchase of common stock (in shares)		1,887,915
Number of common stock reserved for future grants (in shares)		433,201
2012 Plan \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)		2,437,539
2012 Plan \| Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)		2,017,817
Recognized compensation expense \| $		$ 200	$ 400
Prior Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase of common stock (in shares)		972,566
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)		939,249						1,000,000
Shares outstanding under ESPP (in shares)		60,751
Recognized compensation expense \| $		$ 79
Director Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock reserved for future grants (in shares)		366,701
Director Plan \| RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)									1,500,000
Purchase of common stock (in shares)		416,868
Minimum \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount rate from market price, offering date		15.00%
Discount rate from market price, purchase date		0.15