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Stock-based Compensation Plans - Additional Information 4 (Detail) - USD ($)
shares in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]                      
Maximum percentage of employees contribution                 75.00%    
Maximum percentage of employers contribution in cash                 6.00%    
Employer contribution                 $ 5,100,000 $ 4,700,000 $ 6,100,000
Deferred compensation plan vesting period                 3 years    
Deferred compensation plan $ 14,077,000 $ 9,203,000 $ 14,466,000 $ 13,169,000 $ 11,013,000 $ 11,636,000 $ (25,746,000) $ (16,056,000) $ 50,915,000 $ (19,153,000) $ 77,627,000
Shares held in rabbi trust total 2.9       2.7       2.9 2.7  
Vested shares held in rabbi trust 2.8       2.3       2.8 2.3  
Post-Retirement Medical Plan                      
Defined Benefit Plan Disclosure [Line Items]                      
Expected future benefit payments for the five year period 2018 through 2022 $ 675,000               $ 675,000    
Expected future benefit payments for the five year period 2023 through 2027 638,000               638,000    
Estimated prior service cost amortized from accumulated other comprehensive income into statement of operation in 2018 $ 369,000               $ 369,000