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Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 13, 2019
Financial Instruments and Fair Value [Line Items]
Available-for-sale securities, realized gain	$ 4,600,000	$ 1,300,000	$ 4,000,000.0
Available-for-sale securities, realized loss	300,000	200,000	1,600,000
Aggregate loss of investments with unrealized losses less than one year	70,400,000	23,600,000
Unrealized Gain (loss) on contracts	(2,600,000)	1,600,000	$ 2,500,000
Equity securities unrealized gain	9,600,000	5,300,000
Equity securities unrealized loss	$ 6,000,000.0	$ 400,000
Accounts Receivable | Customer 1 | Minimum
Financial Instruments and Fair Value [Line Items]
Concentration risk, percentage	25.00%
Accounts Receivable | Customer 2 | Minimum
Financial Instruments and Fair Value [Line Items]
Concentration risk, percentage		10.00%
Debt Mutual Funds
Financial Instruments and Fair Value [Line Items]
Available for sale securities with out contractual maturity date	$ 8,600,000
Autoguide LLC [Member]
Financial Instruments and Fair Value [Line Items]
Maximum amount of contingent consideration paid for acquisition	100,200,000			$ 100,200,000
Foreign Exchange Contracts
Financial Instruments and Fair Value [Line Items]
Unrealized Gain (loss) on contracts	$ 400,000	$ 300,000

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount before tax of foreign currency transaction unrealized gain (loss) recognized in the income statement.

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