Financial Instruments Investments in Marketable Debt Securities - Schedule of Investments in available-for-sale Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		$ 37,642
Available-for-sale, Unrealized Gains		10
Available-for-sale, Unrealized Losses		(11)
Available-for-sale, Fair Value		37,641
Current Assets
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 7,920	36,141
Available-for-sale, Unrealized Gains	5	10
Available-for-sale, Unrealized Losses	0	(7)
Available-for-sale, Fair Value	7,925	36,144
Current Assets \| Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		1,007
Available-for-sale, Unrealized Gains		0
Available-for-sale, Unrealized Losses		0
Available-for-sale, Fair Value		1,007
Current Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		2,752
Available-for-sale, Unrealized Gains		0
Available-for-sale, Unrealized Losses		(4)
Available-for-sale, Fair Value		2,748
Current Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	7,920	32,382
Available-for-sale, Unrealized Gains	5	10
Available-for-sale, Unrealized Losses	0	(3)
Available-for-sale, Fair Value	$ 7,925	32,389
Noncurrent Assets
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		1,501
Available-for-sale, Unrealized Gains		0
Available-for-sale, Unrealized Losses		(4)
Available-for-sale, Fair Value		1,497
Noncurrent Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		1,501
Available-for-sale, Unrealized Gains		0
Available-for-sale, Unrealized Losses		(4)
Available-for-sale, Fair Value		$ 1,497

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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