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Investments - Investments Classified as Long-Term Available-for-Sale Investments and Long-Term Cost Method Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities and Cost-method Investments [Line Items]
Investments classified as long-term	$ 10,404	$ 10,655
Group Insurance Contracts [Member]
Schedule of Available-for-sale Securities and Cost-method Investments [Line Items]
Investments classified as long-term	6,004	6,255
Minority Interest in Private Company [Member]
Schedule of Available-for-sale Securities and Cost-method Investments [Line Items]
Investments classified as long-term	$ 4,400	$ 4,400

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- Definition

Schedule of available-for-sale securities and cost-method investments.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26626-111562

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- Definition

Amount of investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

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