Cash, cash equivalents, short term and long term investments.

No definition available.

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- Definition

Amount of investments in debt securities classified as available-for-sale, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26626-111562

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- Definition

Total of debt securities categorized neither as held-to-maturity nor trading which are intended be sold or mature more than one year from the balance sheet date or operating cycle, if longer.

+ References

+ Details

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- Definition

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3044-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

No definition available.

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- 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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- Details

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Cash, Cash Equivalents, and Investments - Components of Cash, Cash Equivalents, and Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Oct. 01, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cash	$ 104,654	$ 97,951
Money market instruments	2,717	8,631
Cash and cash equivalents	107,371	106,582	$ 111,349	$ 79,641
Short-term investments	420,016	297,961
Long-term investments	281,929	423,441
Total	809,316	827,984
Treasury Bills
Schedule of Available-for-sale Securities [Line Items]
Short-term investments	193,347	150,371
Long-term investments	32,711	23,459
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Short-term investments	138,099	47,395
Long-term investments	176,007	296,014
Asset-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Short-term investments	71,438	59,203
Long-term investments	60,111	71,727
Sovereign Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Short-term investments	8,119	21,579
Sovereign Bonds
Schedule of Available-for-sale Securities [Line Items]
Long-term investments	6,318	13,147
Agency Bonds
Schedule of Available-for-sale Securities [Line Items]
Short-term investments	2,969	10,608
Long-term investments	5,940	14,890
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Short-term investments	6,044	8,805
Long-term investments	$ 842	$ 4,204