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Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)
 3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Supplemental profit sharing plan $ 5,273,000   $ 4,946,000
Marketable securities 2,281,000   1,648,000
Other Income [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Gain loss on change in fair value of securities 100,000    
Other Income [Member] | Maximum [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Gain loss on change in fair value of securities   $ 100,000  
Profit Sharing Plan [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Supplemental profit sharing plan 5,300,000   4,900,000
Other Assets [Member] | Corporate Owned Life Insurance Policy [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Cash surrender value $ 3,000,000   $ 2,800,000