Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Principles and Practices - Additional Information (Detail)

v2.4.0.8
Summary of Significant Accounting Principles and Practices - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2013
Segment
Contract
Location
Reporting_Unit
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Schedule Of Accounting Policies [Line Items]        
Number of Primary locations 12      
Reportable segments 2      
Significant contracts 0      
Research and development, design and related engineering $ 52,800,000 $ 44,900,000 $ 36,100,000  
Period of options granted 5 years      
Options granted 20.00%      
Excess tax benefits from share based payment arrangements 1,198,000 1,252,000 1,614,000  
Depreciation expense 5,700,000 4,400,000 4,000,000  
Number of reporting units 9      
Number of reporting units have goodwill and subject to goodwill impairment test 6      
Goodwill impairment charge 0 0 2,400,000 0
Cash dividends 0      
Acquisition expenses 1,900,000      
Test Systems Segment [Member]
        
Schedule Of Accounting Policies [Line Items]        
Revenue recognized from long-term, fixed-price contracts 4,400,000 4,200,000 10,000,000  
Goodwill impairment charge      $ 2,400,000  
UNITED STATES
        
Schedule Of Accounting Policies [Line Items]        
Number of Primary locations 10      
Canada [Member]
        
Schedule Of Accounting Policies [Line Items]        
Number of Primary locations 1      
FRANCE
        
Schedule Of Accounting Policies [Line Items]        
Number of Primary locations 1      
Buildings [Member] | Minimum [Member]
        
Schedule Of Accounting Policies [Line Items]        
Property, plant and equipment, useful life 25 years      
Buildings [Member] | Maximum [Member]
        
Schedule Of Accounting Policies [Line Items]        
Property, plant and equipment, useful life 40 years      
Machinery and Equipment [Member] | Minimum [Member]
        
Schedule Of Accounting Policies [Line Items]        
Property, plant and equipment, useful life 4 years      
Machinery and Equipment [Member] | Maximum [Member]
        
Schedule Of Accounting Policies [Line Items]        
Property, plant and equipment, useful life 10 years      
Convertible Class B Stock [Member]
        
Schedule Of Accounting Policies [Line Items]        
Stock distribution One-for-five