Annual report pursuant to Section 13 and 15(d)

Revenue - Narrative (Details)

v3.10.0.1
Revenue - Narrative (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Jan. 01, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Capitalized fulfillment costs $ 9,600  
Amortization of fulfillment cost 1,000  
Contract Liabilities 27,347 $ 11,431
Revenue recognized included in contract liability balance 8,100  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Remaining performance obligation $ 352,400  
Period of recognition 12 months  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Remaining performance obligation $ 415,500  
Test Systems | Held for Sale | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Remaining performance obligation $ 12,200