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Investments - Contractual Maturities of Debt Securities and Other Investments (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, Fair Value/Carrying Value	$ 42,632	$ 37,700	$ 37,660
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	5,441
One to two years	2,926
Two to three years	5,547
Available-for-sale debt securities, Fair Value/Carrying Value	13,914		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	738
One to two years	528
Two to three years	757
Three to five years	377
Available-for-sale debt securities, Fair Value/Carrying Value	2,400		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	465
One to two years	465
Two to three years	1,141
Three to five years	3,932
Five to ten years	982
More than ten years	697
Available-for-sale debt securities, Fair Value/Carrying Value	7,682		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	146
One to two years	603
Two to three years	1,528
Five to ten years	1,890
More than ten years	3,917
Available-for-sale debt securities, Fair Value/Carrying Value	8,084		6,962
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	1,638
Two to three years	6,065
Three to five years	443
Available-for-sale debt securities, Fair Value/Carrying Value	8,146		12,323
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	75
Two to three years	465
Available-for-sale debt securities, Fair Value/Carrying Value	540		371
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	1,124
Available-for-sale debt securities, Fair Value/Carrying Value	1,124
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
More than ten years	300
Available-for-sale debt securities, Fair Value/Carrying Value	300		$ 800
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	442
Available-for-sale debt securities, Fair Value/Carrying Value	$ 442

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