Term Receivables and Trade Accounts Receivable - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
Jul. 31, 2015	Jul. 31, 2014
Disclosure Term Receivables And Trade Accounts Receivable Additional Information [Abstract]
Billing period	30 days
Net proceeds from sale of receivables	$ 27,562	$ 11,405
Allowance for doubtful accounts adjustment
Valuation Allowances and Reserves, Charged to Cost and Expense		$ (1,691)

Number of days prior to contractual due date that term billings typically occur.

No definition available.

Name:	ment_BillingPeriod
Namespace Prefix:	ment_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Disclosure - Term Receivables and Trade Accounts Receivable - Additional Information [Abstract]

+ References

No definition available.

+ Details

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

- Definition

The cash inflow associated with the sale of receivables arising from the financing of goods and services.

+ References

No definition available.

+ Details

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

- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, charged to costs and expenses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Article 12

+ Details

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

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=ment_MentAllowanceForDoubtfulAccountsAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: