[Line Items] for Income Taxes [Table]

No definition available.

Name:	ment_IncomeTaxesLineItems
Namespace Prefix:	ment_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of benefit due to the release of an accrual for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

No definition available.

+ Details

Name:	ment_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestBenefit
Namespace Prefix:	ment_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (d)(3)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

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

- Definition

The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from employee benefit costs not otherwise specified in the taxonomy, which can only be deducted for tax purposes when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32621-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51675352&loc=d3e28680-109314

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32632-109319

+ Details

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

- Definition

Tax year that remains open to examination under enacted tax laws, in CCYY format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

Name:	us-gaap_OpenTaxYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of undistributed earnings of foreign subsidiaries intended to be permanently reinvested outside the country of domicile.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 740
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6487024&loc=d3e29054-158556

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 740
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6479915&loc=d3e66715-112838

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 995
-SubTopic 740
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6503627&loc=d3e59836-110443

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=51675352&loc=d3e28200-109314

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(c)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

+ Details

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

- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

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

- Definition

Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

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

- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

+ Details

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

- Details

Name:	us-gaap_TaxPeriodAxis=us-gaap_EarliestTaxYearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ment_MajorTaxJurisdictionsYearsOpenForExaminationAxis=us-gaap_DomesticCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ment_MajorTaxJurisdictionsYearsOpenForExaminationAxis=ment_IrelandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ment_MajorTaxJurisdictionsYearsOpenForExaminationAxis=ment_JapanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ment_MajorTaxJurisdictionsYearsOpenForExaminationAxis=ment_IndiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ment_MajorTaxJurisdictionsYearsOpenForExaminationAxis=ment_IsraelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TaxPeriodAxis=us-gaap_LatestTaxYearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Income Taxes
Deferred tax assets, tax deferred expense, compensation and benefits, employee benefits	$ 48,591	$ 43,206
Undistributed earnings of foreign subsidiaries	461,438
Unrecognized tax benefits, income tax penalties and interest expense	1,717	884
Unrecognized tax benefits, income tax penalties And interest (benefit)			$ (1,710)
Income tax penalties and interest accrued	9,817	$ 8,366
Unrecognized tax benefits that would impact effective tax rate	$ 25,162
Earliest Tax Year \| Domestic Tax Authority
Income Taxes
Open tax year	2013
Earliest Tax Year \| Ireland
Income Taxes
Open tax year	2012
Earliest Tax Year \| Japan
Income Taxes
Open tax year	2011
Earliest Tax Year \| India
Income Taxes
Open tax year	2009
Earliest Tax Year \| Israel
Income Taxes
Open tax year	2012
Latest Tax Year \| Domestic Tax Authority
Income Taxes
Open tax year	2016
Latest Tax Year \| Ireland
Income Taxes
Open tax year	2016
Latest Tax Year \| Japan
Income Taxes
Open tax year	2016
Latest Tax Year \| India
Income Taxes
Open tax year	2016
Latest Tax Year \| Israel
Income Taxes
Open tax year	2016
Minimum
Income Taxes
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 0
Maximum
Income Taxes
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 3,000