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Nature of Business - Additional Information (Detail)
 3 Months Ended 6 Months Ended 12 Months Ended
Jan. 01, 2019
USD ($)
Jun. 30, 2019
USD ($)
Jun. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Customer
IncentivePlan
Dec. 31, 2018
USD ($)
Customer
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Summary Of Significant Accounting Policy [Line Items]              
Cash, uninsured amount       $ 71,600,000      
Bonds payable, carrying amount       24,600,000      
Bonds payable, fair value       $ 24,600,000      
Number of single customer comprising more than 10% of account receivable | Customer       4 2    
Allowance for doubtful accounts       $ 38,000 $ 128,000    
Asset impairments       3,872,000 0 $ 0  
Impairment charges recognized on goodwill       $ 0 0 0  
Period of assurance-based warranty for product defects       90 days to five years      
Liability for warranty obligations       $ 8,394,000 8,623,000 9,724,000 $ 8,548,000
Pension liability       $ 15,886,000 13,086,000    
Number of stock incentive plans | IncentivePlan       2      
Stock-based compensation expense       $ 6,962,000 7,155,000 7,433,000  
Total unrecognized compensation cost related to non-vested stock options, PSUs, RSUs and restricted stock       $ 17,200,000      
Recognition period of unvested compensation expense       3 years      
Research and development costs       $ 126,200,000 124,547,000 $ 130,666,000  
Operating lease, right-of-use asset $ 10,322,000     8,452,000      
Operating lease, right-of-use liability 10,322,000     8,494,000      
Prepaid Expenses and Other Current Assets [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Current deferred costs related to prepaid and other assets       1,600,000 2,400,000    
Other Assets [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Non-current deferred costs related to other assets       $ 100,000 $ 800,000    
ASU 2018-02 [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Reclassification of tax effects related to adoption ASU $ 400,000            
Minimum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Amortization, estimated useful lives       2 years      
Lessor sales type lease arrangement terms for network equipments       18 months      
Maintenance service periods       1 month      
Maintenance contract period       1 month      
Maximum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Amortization, estimated useful lives       14 years      
Lessor sales type lease arrangement terms for network equipments       5 years      
Maintenance service periods       5 years      
Maintenance contract period       5 years      
Maximum [Member] | Accounting Policy under Topic 605 [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Invoiced sales tax as percentage on total revenues.       1.00%      
Building and Land Improvements [Member] | Minimum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       5 years      
Building and Land Improvements [Member] | Maximum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       39 years      
Office Machinery and Equipment [Member] | Minimum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       3 years      
Office Machinery and Equipment [Member] | Maximum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       7 years      
Engineering Machinery and Equipment [Member] | Minimum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       3 years      
Engineering Machinery and Equipment [Member] | Maximum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       7 years      
Computer Software [Member] | Minimum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       3 years      
Computer Software [Member] | Maximum [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Property, plant and equipment, estimated useful lives       5 years      
Credit Concentration Risk [Member] | Accounts Receivable [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Percentage of accounts receivable accounted by each customers       53.20% 36.90%    
Out-of-Period Adjustment [Member]              
Summary Of Significant Accounting Policy [Line Items]              
Increase (decrease) in cost of goods sold   $ 800,000 $ (200,000)        
Increase (decrease) in excess and obsolete inventory reserve   $ 800,000 $ (200,000)