Term Receivable and Trade Accounts Receivable Balances Transfer of Financial Assets Accounted for as Sales (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Transfer of Financial Assets Accounted for as Sales
Proceeds from Sale of Finance Receivables	$ 42,661	$ 22,572	$ 22,943
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	44,114	23,176	23,617
Discount on sold receivables	(1,453)	(604)	(674)
Unaccreted Interest on Sold Receivables Net	2,723	922	890
Gain (Loss) on Sale of Accounts Receivable	1,270	318	216
Trade accounts receivable
Transfer of Financial Assets Accounted for as Sales
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	16,344	12,715	11,705
Term Receivables Long Term
Transfer of Financial Assets Accounted for as Sales
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	$ 27,770	$ 10,461	$ 11,912

The discount recognized during the period on the sale of receivables.

No definition available.

Name:	ment_DiscountsonSoldReceivables
Namespace Prefix:	ment_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of unaccreted interest on sold receivables recognized during the period.

+ References

No definition available.

+ Details

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

- Definition

Reflects the net positive or negative amount derived from subtracting from net proceeds of sale, the carrying amounts, net of allocated reserves, of accounts receivable transferred to a third party in a transaction that qualifies for sales treatment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=51814546&loc=d3e107425-111719

+ Details

Name:	us-gaap_GainLossOnSaleOfAccountsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Amount of derecognized financial assets from transactions which comprise an initial transfer and an agreement entered into in contemplation of the initial transfer resulting in retention of substantially all of the exposure to the economic return throughout the term of the transaction, at the date of derecognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51814546&loc=SL51823488-111719

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_TradeAccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=ment_TermReceivablesLongTermMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: