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Investments - Contractual Maturities of Debt Securities and Other Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 45,515	$ 45,116
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	275
One to two years	4,494
Two to three years	6,616
Three to five years	2,029
Available-for-sale debt securities, Fair Value/Carrying Value	13,414	11,885
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	652
One to two years	534
Two to three years	761
Three to five years	301
Available-for-sale debt securities, Fair Value/Carrying Value	2,248	2,884
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Two to three years	93
Three to five years	1,573
Five to ten years	785
More than ten years	1,062
Available-for-sale debt securities, Fair Value/Carrying Value	3,513	6,708
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	638
One to two years	1,005
Two to three years	1,102
Three to five years	235
Five to ten years	1,322
More than ten years	4,910
Available-for-sale debt securities, Fair Value/Carrying Value	9,212	11,644
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	2,593
One to two years	4,021
Two to three years	5,810
Three to five years	3,628
Available-for-sale debt securities, Fair Value/Carrying Value	16,052	9,875
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	246
Two to three years	297
Available-for-sale debt securities, Fair Value/Carrying Value	543	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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Amount of available-for-sale debt securities at fair value maturing after one year through two years.

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