Assets accumulated gross unrealized gain before tax.

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- Definition

Assets accumulated gross unrealized loss before tax.

+ References

No definition available.

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- Definition

Assets amortized cost.

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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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Fair value portion 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.

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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.

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Marketable Securities - Schedule of Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 29,894	$ 22,061	$ 27,986	$ 69,482
Amortized Cost	237,946	139,416
Gross Unrealized Gains	2	76
Gross Unrealized (Losses)	(103)	(26)
Estimated Fair Value	237,845	139,466
Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	223,236	120,424
Gross Unrealized Gains	2	76
Gross Unrealized (Losses)	(103)	(26)
Estimated Fair Value	223,135	120,474
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	14,710	18,992
Total cash equivalents	14,710	18,992
Cash equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	14,710	18,992
Total cash equivalents	14,710	18,992
Commercial paper securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	106,759	23,112
Gross Unrealized Gains	2	73
Gross Unrealized (Losses)	(34)
Estimated Fair Value	106,727	23,185
Corporate debt securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	80,177	10,005
Gross Unrealized (Losses)	(51)	(1)
Estimated Fair Value	80,126	10,004
U.S. government-sponsored entity debt securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	36,300	87,307
Gross Unrealized Gains		3
Gross Unrealized (Losses)	(18)	(25)
Estimated Fair Value	$ 36,282	$ 87,285