Operating Segment, Geographic And Significant Customer Information (Narrative) (Details)	12 Months Ended
Dec. 31, 2011 segments	Dec. 31, 2009 Systems Test Group [Member]
Segment Reporting Information [Line Items]
Number of reportable operating segments	3
Major customer, approximate percentage of total revenue		13.00%

Percent of total consolidated revenue accounted for by major customer for segment reporting

No definition available.

Name:	ter_SegmentReportingMajorCustomersPercentRevenue
Namespace Prefix:	ter_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration