Percentage of principal for which we may redeem some or all of the debentures for cash after a specified date.

No definition available.

Name:	ment_DebenturesRedemptionPrice
Namespace Prefix:	ment_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares to be issued in exchange for the original debt being converted in a noncash (or part noncash) transaction.

+ References

No definition available.

+ Details

Name:	ment_DebtConversionConvertedInstrumentSharesToBeIssued
Namespace Prefix:	ment_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument Amortization, End Date

+ References

No definition available.

+ Details

Name:	ment_DebtInstrumentAmortizationEndDate
Namespace Prefix:	ment_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage by which the market price of the debentures as a percentage of the value of the common stock into which the debentures are convertible must decline for the debentures to be convertible into common stock.

+ References

No definition available.

+ Details

Name:	ment_DebtInstrumentConversionCircumstancePercentageDebenturePriceOfStockThreshold
Namespace Prefix:	ment_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage by which the market price of common stock must exceed the conversion price for the debentures to be convertible into common stock.

+ References

No definition available.

+ Details

Name:	ment_DebtInstrumentConversionCircumstancePercentageStockPriceOfStockConversionThreshold
Namespace Prefix:	ment_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 32

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The effective interest rate on the liability component of convertible debt instrument which may be settled in cash upon conversion, including partial cash settlement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 6

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6036836-161870

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 33

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleEffectiveInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Interest rate stated in the contractual debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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

Notes Payable - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Debt Instrument [Line Items]
Interest rate			4.00%
4.00% Debentures due 2031 \| Convertible Subordinated Debt
Debt Instrument [Line Items]
Debt instrument amortization end date	2018-03
Issued debt			$ 253,000
Convertible debentures to common stock, conversion price	$ 20.538
Convertible debentures to common stock, total number of share	12,319
Market price of common stock exceeding percent of the conversion price	120.00%
Market price of debentures declining to maximum percent of the value of the common stock	98.00%
Effective Interest Rate	7.25%	7.25%
Holder optional redemption period 1 [Member] \| 4.00% Debentures due 2031 \| Convertible Subordinated Debt
Debt Instrument [Line Items]
Debentures redemption price	100.00%
Holder optional redemption period 2 [Member] \| 4.00% Debentures due 2031 \| Convertible Subordinated Debt
Debt Instrument [Line Items]
Debentures redemption price	100.00%
Holder optional redemption period 3 [Member] \| 4.00% Debentures due 2031 \| Convertible Subordinated Debt
Debt Instrument [Line Items]
Debentures redemption price	100.00%