This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of deferred compensation liability as of the balance sheet date.

No definition available.

+ Details

Name:	mpaa_DeferredCompensationFairValueDisclosure
Namespace Prefix:	mpaa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CC
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998890-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value portion of asset contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward contracts, and swaps.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Fair Value Measurements (Details) - USD ($)	3 Months Ended		6 Months Ended
Fair Value Measurements (Details) - USD ($)	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Forward Foreign Currency Exchange Contracts [Member]
Other current liabilities [Abstract]
Net gain (loss) on forward foreign currency exchange contracts	$ 1,898,000	$ (330,000)	$ (768,000)	$ 722,000
Recurring [Member]
Short-term investments [Abstract]
Mutual funds	3,230,000		3,230,000		$ 2,828,000
Prepaid expenses and other current assets [Abstract]
Forward foreign currency exchange contracts	411,000		411,000		1,179,000
Other current liabilities [Abstract]
Deferred compensation	3,230,000		3,230,000		2,828,000
Recurring [Member] \| Level 1 [Member]
Short-term investments [Abstract]
Mutual funds	3,230,000		3,230,000		2,828,000
Prepaid expenses and other current assets [Abstract]
Forward foreign currency exchange contracts	0		0		0
Other current liabilities [Abstract]
Deferred compensation	3,230,000		3,230,000		2,828,000
Recurring [Member] \| Level 2 [Member]
Short-term investments [Abstract]
Mutual funds	0		0		0
Prepaid expenses and other current assets [Abstract]
Forward foreign currency exchange contracts	411,000		411,000		1,179,000
Other current liabilities [Abstract]
Deferred compensation	0		0		0
Recurring [Member] \| Level 3 [Member]
Short-term investments [Abstract]
Mutual funds	0		0		0
Prepaid expenses and other current assets [Abstract]
Forward foreign currency exchange contracts	0		0		0
Other current liabilities [Abstract]
Deferred compensation	$ 0		$ 0		$ 0