Organization and Basis of Presentation (Details) - May. 31, 2015 - USD ($)	Total
Pending Merger With Intel Corporation [Line Items]
Business Acquisition, Share Price	$ 54.00
Termination Fee, Merger Agreement	$ 500,000,000
Maximum Expense Reimbursement, Merger Agreement Termination	$ 60,000,000

Maximum expense reimbursement to the other party due to termination of merger agreement

No definition available.

Name:	altr_MaximumExpenseReimbursementMergerAgreementTermination
Namespace Prefix:	altr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant