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Pension Plans - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pension And Other Employee Benefit Plans [Line Items]      
Estimated net loss for the PLP-USA pension plan in 2018 $ 200,000    
Prior service cost 0    
Pre-tax unfunded pension obligation gain (loss) $ (700,000)    
Discount rate 3.75% 4.25%  
Asset performance rate of return assumption 8.00%    
Expected long-term return on plan assets 8.00% 8.00% 8.00%
Contribution to pension plan $ 0    
Expense for contribution plan $ 5,100,000 $ 5,800,000 $ 5,500,000
Weighted average of one year treasury bill 1.00%    
Interest rate for the supplemental profit sharing plan 2.76% 1.65%  
Expense for the supplemental profit sharing plan $ 500,000 $ 500,000 $ 300,000
Supplemental profit sharing plan unfunded status 4,800,000 $ 4,300,000  
Reduction in Discount Rate [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) $ (2,800,000)    
Discount rate 0.50%    
Gain on Industry Updates to Mortality Table [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) $ 300,000    
Demographic Changes [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) 200,000    
Asset Performance [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) $ 1,600,000