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Investments - Contractual Maturities of Debt Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 37,660	$ 40,799
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	4,005
One to two years	4,120
Two to three years	967
Three to five years	292
Available-for-sale debt securities, Fair Value/Carrying Value	9,384	20,684
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	930
Available-for-sale debt securities, Fair Value/Carrying Value	930	1,313
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	396
One to two years	760
Two to three years	1,632
Three to five years	2,092
Five to ten years	1,719
More than ten years	291
Available-for-sale debt securities, Fair Value/Carrying Value	6,890	5,221
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	213
Two to three years	1,424
Three to five years	494
Five to ten years	792
More than ten years	4,039
Available-for-sale debt securities, Fair Value/Carrying Value	6,962	3,791
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	1,347
Two to three years	9,344
Three to five years	1,632
Available-for-sale debt securities, Fair Value/Carrying Value	12,323	9,206
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Three to five years	371
Available-for-sale debt securities, Fair Value/Carrying Value	$ 371	$ 584

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