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Organization and Significant Accounting Policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2017
USD ($)
Segment
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2015
USD ($)
shares
Significant Accounting Policies [Line Items]      
Impairment of long-lived asset $ 0 $ 0 $ 0
Date of annual test of impairment for goodwill On October 1st of each year.    
Number of operating segments | Segment 1    
Impairment of goodwill $ 0    
Impairment of intangible assets 0 0 0
Amount of grants recorded as reduction in research and development expense 4,417,000 6,410,000 4,997,000
Tax credits on research and development expenses $ 1,555,000 1,485,000 1,414,000
Pension contribution rate 10.00%    
Percentage of match made by the employer up to a maximum of 6% 100.00%    
Maximum percentage contribute by each participant from base remuneration 15.00%    
Employee plan contribution $ 988,000 1,020,000 733,000
Severance pay expense, net of related income $ 1,413,000 1,348,000 1,285,000
Number of shares, Options/SAR units granted | shares [1] 0    
Impairment loss $ 0    
Advertising expense $ 1,118,000 $ 1,033,000 $ 928,000
Antidilutive shares excluded from computation of earnings per share | shares 29,892 282,696 820,631
Foreign exchange forward and option contracts | Derivatives designated as cash flow hedging instruments      
Significant Accounting Policies [Line Items]      
Notional principal amount of Hedging Contracts $ 0 $ 3,300,000  
Minimum      
Significant Accounting Policies [Line Items]      
Intangible assets definite lives 1 year 6 months    
Royalty expenses percentage 3.00%    
Maximum      
Significant Accounting Policies [Line Items]      
Intangible assets definite lives 5 years 6 months    
Royalty expenses percentage 3.50%    
Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan 6.00%    
Royalty Revenue | ASU 2014-09      
Significant Accounting Policies [Line Items]      
Revenues recognized from sales-based royalties $ 8,765,000    
Stock Options, Stock Appreciation Rights and Employee Stock Purchase Plan      
Significant Accounting Policies [Line Items]      
Unrecognized compensation expense $ 620,000    
Unrecognized compensation expense, weighted-average period of recognition 1 year 3 months 19 days    
Restricted Stock Units (RSUs)      
Significant Accounting Policies [Line Items]      
Unrecognized compensation expense $ 10,894,000    
Unrecognized compensation expense, weighted-average period of recognition 1 year 4 months 24 days    
Retained Earnings | ASU 2014-09      
Significant Accounting Policies [Line Items]      
Cumulative adjustment to increase in equity or assets $ 8,055,000    
Assets | ASU 2014-09      
Significant Accounting Policies [Line Items]      
Cumulative adjustment to increase in equity or assets 9,117,000    
Current Liabilities | ASU 2014-09      
Significant Accounting Policies [Line Items]      
Cumulative adjustment to increase in equity or assets $ 1,062,000    
Short-term investments      
Significant Accounting Policies [Line Items]      
Interest rate bank deposits 1.85% 1.76% 1.51%
Long-term investments      
Significant Accounting Policies [Line Items]      
Interest rate bank deposits 2.26% 1.97% 1.82%
[1] The SAR units are convertible for a maximum number of shares of the Company's common stock equal to 75% of the SAR units subject to the grant.