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Investments - Cash Equivalents and Investments held at Fair Value (Detail) - USD ($)
Sep. 30, 2023
Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities $ 0 $ 9,253,000
Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash equivalents 5,245,000 228,000
Total short-term and long-term investments 25,179,000 33,005,000
Total 30,424,000 33,233,000
Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash equivalents 5,245,000 228,000
Total short-term and long-term investments 25,179,000 27,437,000
Total 30,424,000 27,665,000
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Total short-term and long-term investments   5,568,000
Total   5,568,000
Money Market Funds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash equivalents 5,245,000 228,000
Money Market Funds [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash equivalents 5,245,000 228,000
Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   2,462,000
Corporate Bonds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   2,462,000
Corporate Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   2,462,000
Municipal Fixed-Rate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   180,000
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   180,000
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   180,000
Asset-Backed Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   795,000
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   795,000
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   795,000
Mortgage/Agency-Backed Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   1,748,000
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   1,748,000
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   1,748,000
U.S. Government Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   3,685,000
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   3,685,000
U.S. Government Bonds [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   3,685,000
Foreign Government Securities / Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   383,000
Foreign Government Securities / Bonds [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   383,000
Foreign Government Securities / Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale debt securities   383,000
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Marketable equity securities 815,000 810,000
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Marketable equity securities 815,000 810,000
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Marketable equity securities 24,364,000 22,942,000
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Marketable equity securities $ 24,364,000 $ 22,942,000