Accounts Receivable Discount Programs (Details) (USD $)	9 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Accounts Receivable Discount Programs [Abstract]
Receivables discounted	$ 229,314,000	$ 197,019,000
Weighted average days	316 days	314 days
Annualized weighted average discount rate (in hundredths)	2.80%	2.90%
Amount of discount as interest expense	$ 5,525,000	$ 4,984,000

Represents the weighted average number of days these discount arrangements have allowed the Company to accelerate collection of discounted accounts receivable balances during the period.

No definition available.

Name:	mpaa_DiscountedAccountsReceivableWeightedAverageDaysForAcceleratedCollection
Namespace Prefix:	mpaa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration