Balance Sheet Components - Summary of Cash Equivalents and Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Cash Equivalents and Available-for-Sale Securities [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	$ 85,241	$ 10,009
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	2
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses	(74)	(5)
Total cash equivalents and available-for-sale securities, Fair Value	85,169	10,004
Cash equivalents	18,504	2,136
Available-for-sale securities - current	56,515	7,868
Available-for-sale securities - noncurrent	10,150
Corporate Bonds Member]
Cash Equivalents and Available-for-Sale Securities [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	21,886	7,373
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses	(45)	(5)
Total cash equivalents and available-for-sale securities, Fair Value	21,841	7,368
Governmental Bonds [Member]
Cash Equivalents and Available-for-Sale Securities [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	41,316
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	2
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses	(29)
Total cash equivalents and available-for-sale securities, Fair Value	41,289
Money Market Funds [Member]
Cash Equivalents and Available-for-Sale Securities [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	11,270	2,136
Total cash equivalents and available-for-sale securities, Fair Value	11,270	2,136
Commercial Paper [Member]
Cash Equivalents and Available-for-Sale Securities [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	10,769	500
Total cash equivalents and available-for-sale securities, Fair Value	$ 10,769	$ 500

Cash equivalents and available for sale securities amortized cost.

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- Definition

Cash equivalents and available for sale securities fair value.

+ References

No definition available.

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- Definition

Cash equivalents and available for sale securities gross unrealized gain.

+ References

No definition available.

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- Definition

Cash equivalents and available for sale securities gross unrealized loss.

+ References

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- Definition

Cash equivalents and available-for-sale securities.

+ References

No definition available.

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- Definition

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or 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=65884222&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=66010992&loc=d3e26626-111562

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Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Available-for-Sale Securities
-URI http://asc.fasb.org/extlink&oid=6505594

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=66010992&loc=d3e26626-111562

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- Definition

Amount of 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 S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

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