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Short-Term and Long-Term Investments - Summary of Available-for-Sale Securities (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
US Treasury Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	$ 70,172,000
Gross Unrealized Losses	8,000
Estimated Fair Value	70,164,000
Failed Auction Security [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	3,000,000	$ 3,000,000
Gross Unrealized Losses	483,000	490,000
Estimated Fair Value	$ 2,517,000	$ 2,510,000

X

- Definition

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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

+ Details

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X

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

+ Details

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X

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

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X

- Definition

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.

+ Details

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- Details

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