Stock-Based Compensation - Outstanding Stock Options (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2014
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Outstanding	$ 2.30
Shares, Outstanding	258,723
Weighted-Average Life (Years), Outstanding	4 years 7 months 2 days
Intrinsic Value, Outstanding	$ 1,405
Stock Options Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Outstanding	$ 5.77
Shares, Outstanding	31,923
Weighted-Average Life (Years), Outstanding	2 years 7 months 24 days
Intrinsic Value, Outstanding	62
Stock Options Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Outstanding	$ 5.85
Shares, Outstanding	142,382
Weighted-Average Life (Years), Outstanding	3 years 7 months 6 days
Intrinsic Value, Outstanding	268
Stock Options Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding	433,028
Weighted-Average Life (Years), Outstanding	4 years 1 month 13 days
Intrinsic Value, Outstanding	$ 1,735

Intrinsic values outstanding at stock option plan exercise price.

No definition available.

Name:	mfi_IntrinsicValuesOutstandingAtStockOptionPlanExercisePrice
Namespace Prefix:	mfi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-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=6415400&loc=d3e5070-113901

+ Details

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

- Definition

The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

+ References

+ Details

Name:	us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration