Accounting policy.

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Highly liquid investment maturity period.

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Long term investments minimum maturity period.

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Restricted time deposits noncurrent.

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Short term investments maximum maturity period.

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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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No definition available.

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Amount of the related income tax effect of a cumulative effect on retained earnings.

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The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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Represents the quantification of the effect of adopting the new accounting standard or change in accounting principle expected by the entity to have a significant effect on the entity's financial statements.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 01, 2015 USD ($)
Accounting Policy [Line Items]
Number of operating segment \| Segment	1
Highly liquid investment maturity period	three months or less
Restricted time deposits	$ 5,181,000	$ 6,217,000
Cash and cash equivalents	$ 673,658,000	173,782,000	$ 153,324,000	$ 165,455,000
Long term Investments Maturity	12 months
Short term investments Maturity	12 months
Impairment of long-lived assets	$ 0
Increase in valuation allowance	30,500,000	12,300,000		$ 22,000,000
New Revenue Standards [Member] \| Revenue [Member]
Accounting Policy [Line Items]
Increase (reduction) in revenue	5,300,000	$ 3,600,000	$ (8,400,000)
ASU 2016-09 [Member]
Accounting Policy [Line Items]
Retrospective increase in deferred tax assets for previously unrecognized excess tax benefits	19,500,000
Increase in valuation allowance	19,500,000
Net impact to accumulated deficit	$ 0
ASU 2014-09 [Member] \| Accumulated Deficit [Member]
Accounting Policy [Line Items]
Increase in accumulative deficit					$ 35,200,000
Minimum [Member] \| Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Minimum [Member] \| Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Minimum [Member] \| Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	3 years
Maximum [Member] \| Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Maximum [Member] \| Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Maximum [Member] \| Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life	5 years
Foreign subsidiaries [Member]
Accounting Policy [Line Items]
Cash and cash equivalents	$ 32,300,000