Available-for-sale Securities and Fair Value on Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities in unrealized net loss position	$ 0	$ 283,000
Other-than-temporary impairment losses	$ 0	$ 0	$ 0
Remaining investment in common stock	144,291,000	136,853,000
Gross realized losses from the sale or maturity of available-for-sale investments	$ 0	$ 0	0
Aduro Biotech Inc
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains from the sale of available-for-sale investments	$ 0	$ 0	$ 3,500,000
Sale of common stock available-for-sale investments	0	0	346,700
Remaining investment in common stock	0	0

Sale of common stock in marketable equity investment.

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- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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- Definition

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

+ References

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

+ References

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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), in unrealized loss position without allowance for credit loss.

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The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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