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Investments - Fair Value Measurements of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 37,660	$ 40,799
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	98,908	87,625
Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	73,571	56,032
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	25,337	31,593
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,309	1,554
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	1,309	1,554
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,384	20,684
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	9,384	20,684
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 securities	9,384	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	930	1,313
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	930	1,313
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 securities	930	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,890	5,221
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,890	5,221
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 securities	6,890	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,962	3,791
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	6,962	3,791
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 securities	6,962	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	12,323	9,206
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	12,323	9,206
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 securities	12,323	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	371	584
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	371	584
Foreign Government Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	371	584
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	800
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	35,501	26,763
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	35,501	26,763
Equity in Escrow [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	298	253
Equity in Escrow [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	298	253
Other Investments [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	2,442
Other Investments [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	2,442
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	21,698	18,256
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	$ 21,698	$ 18,256

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