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Investments - Contractual Maturities of Debt Securities and Other Investments (Detail) - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale debt securities, Fair Value/Carrying Value | $ 44,480 | $ 45,116
Corporate Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than one year | 436 |
One to two years | 4,575 |
Two to three years | 7,518 |
Three to five years | 2,472 |
Available-for-sale debt securities, Fair Value/Carrying Value | 15,001 | 11,885
Municipal Fixed-Rate Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than one year | 529 |
One to two years | 496 |
Two to three years | 1,103 |
Three to five years | 409 |
Available-for-sale debt securities, Fair Value/Carrying Value | 2,537 | 2,884
Asset-Backed Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than one year | 1 |
Two to three years | 50 |
Three to five years | 1,749 |
Five to ten years | 866 |
More than ten years | 1,335 |
Available-for-sale debt securities, Fair Value/Carrying Value | 4,001 | 6,708
Mortgage/Agency-Backed Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than one year | 254 |
One to two years | 1,865 |
Two to three years | 1,199 |
Three to five years | 165 |
Five to ten years | 2,213 |
More than ten years | 5,343 |
Available-for-sale debt securities, Fair Value/Carrying Value | 11,039 | 11,644
U.S. Government Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than one year | 735 |
One to two years | 7,240 |
Two to three years | 1,188 |
Three to five years | 1,660 |
Available-for-sale debt securities, Fair Value/Carrying Value | 10,823 | 9,875
Foreign Government Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Two to three years | 546 |
Available-for-sale debt securities, Fair Value/Carrying Value | 546 | 1,337
Other [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Less than one year | 533 |
Available-for-sale debt securities, Fair Value/Carrying Value | $ 533 | $ 533

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