Marketable securities (Detail) - USD ($)	Sep. 30, 2022	Apr. 30, 2022	Dec. 31, 2021
Amortized cost / Cost
Equity securities	$ 0		$ 4,305,000
Marketable securities	76,852,000		236,638,000
Unrealized gains
Equity securities	0		0
Marketable securities	0		0
Unrealized losses
Equity securities	0		(614,000)
Marketable securities	(2,290,000)		(1,182,000)
Fair value
Debt securities		$ 29,700,000
Equity securities	0		3,691,000
Marketable securities	74,562,000		235,456,000
Debt securities, available-for-sale, noncurrent	0		0
U.S. government agency securities and treasuries
Amortized cost / Cost
Debt securities	70,456,000		128,902,000
Unrealized gains
Debt securities	0		0
Unrealized losses
Debt securities	(2,215,000)		(509,000)
Fair value
Debt securities	68,241,000		128,393,000
Corporate bonds
Amortized cost / Cost
Debt securities	6,396,000		49,366,000
Unrealized gains
Debt securities	0		0
Unrealized losses
Debt securities	(75,000)		(59,000)
Fair value
Debt securities	6,321,000		49,307,000
Commercial paper
Amortized cost / Cost
Debt securities	0		54,065,000
Unrealized gains
Debt securities	0		0
Unrealized losses
Debt securities	0		0
Fair value
Debt securities	$ 0		$ 54,065,000

Equity securities unrealized gain.

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Equity securities unrealized loss.

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Marketable securities amortized cost.

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Marketable securities unrealized gains.

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Marketable securities unrealized loss.

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

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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Amount of investment in marketable security.

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