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Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Loss in investment interest and other	$ 372
Unrealized gain or loss	0
Unrealized net (losses) gains on available-for-sale securities	$ 0	$ 255
Certificates of Deposit [Member]
Debt Securities, Available-for-sale [Line Items]
Maturity period of investments	one year or less

X

- Definition

Investment maturity period.

+ References

No definition available.

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X

- Definition

Amount of unrealized loss recognized in earnings from transfer of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) to investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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X

- Definition

Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

No definition available.

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X

- Definition

Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

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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.

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X

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