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Employee Benefit Plans - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]      
Employee contribution to Company's profit sharing plan percentage 1.00%    
Employee contribution to Company's profit sharing plan percentage 50.00%    
Minimum age limit for specified additional amount 50 years    
Company's contributions $ 5,651 $ 6,524 $ 2,667
Bonus expense 46,783 28,097 14,599
Supplemental retirement benefits cost 3,478 1,805 $ 1,704
Accumulated benefit obligation 15,929 12,450  
Defined benefit plan assets 8,152    
Defined benefit plan, vested benefit obligations 17,932 16,224  
Defined benefit plan expected future benefit payments $ 2,283    
Expected long-term rate of return on assets 1.90%    
Israel [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan assets $ 15,048 13,910  
Japan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Expected long-term rate of return on assets 1.50%    
United Kingdom [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Expected long-term rate of return on assets 2.60%    
France [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Expected long-term rate of return on assets 1.60%    
Germany [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan assets $ 6,255 $ 5,558  
Germany [Member] | Minimum [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan assets guaranteed rate of return 2.25%    
Germany [Member] | Maximum [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan assets guaranteed rate of return 4.25%