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Investments - Cash Equivalents and Investments held at Fair Value (Detail) - USD ($) $ in Thousands | Jun. 30, 2020 | Jan. 01, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | $ 42,632 | $ 37,700 | $ 37,660
Marketable equity securities | 1,800 |  |
Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Other investments | 1,223 |  | 2,442
Total | 93,486 |  | 98,908
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 | 1,223 |  | 2,442
Total | 58,900 |  | 73,571
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Total | 34,144 |  | 25,337
Fair Value, Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Total | 442 |  |
Money Market Funds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cash equivalents | 1,697 |  | 1,309
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 | 1,697 |  | 1,309
U.S. Government Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 8,146 |  | 12,323
U.S. Government Bonds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cash equivalents | 1,250 |  |
Available-for-sale debt securities | 8,146 |  | 12,323
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] |  |  |
Cash equivalents | 1,250 |  |
Available-for-sale debt securities | 8,146 |  | 12,323
Commercial Paper [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 1,124 |  |
Commercial Paper [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cash equivalents | 100 |  |
Available-for-sale debt securities | 1,124 |  |
Commercial Paper [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cash equivalents | 100 |  |
Available-for-sale debt securities | 1,124 |  |
Corporate Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 13,914 |  | 9,384
Corporate Bonds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 13,914 |  | 9,384
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 | 13,914 |  | 9,384
Municipal Fixed-Rate Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 2,400 |  | 930
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 2,400 |  | 930
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 | 2,400 |  | 930
Asset-Backed Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 7,682 |  | 6,890
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 7,682 |  | 6,890
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 | 7,682 |  | 6,890
Mortgage/Agency-Backed Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 8,084 |  | 6,962
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 8,084 |  | 6,962
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 | 8,084 |  | 6,962
Other [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 442 |  |
Other [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 442 |  |
Other [Member] | Fair Value, Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 442 |  |
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Marketable equity securities | 26,116 |  | 35,501
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 | 26,116 |  | 35,501
Foreign Government Bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 540 |  | 371
Foreign Government Bonds [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 540 |  | 371
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 debt securities | 540 |  | 371
Variable Rate Demand Notes [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 300 |  | 800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Available-for-sale debt securities | 300 |  | 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 debt securities | 300 |  | 800
Equity in Escrow [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Marketable equity securities |  |  | 298
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
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Marketable equity securities | 20,468 |  | 21,698
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 | $ 20,468 |  | $ 21,698

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