Status of Stock Options (Detail) - Employee Stock Option - 2013 and 2017 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Shares
Outstanding	7,507,690	6,514,538
Vested	4,149,238
Weighted-Average Exercise Price Per Share
Outstanding	$ 33.25	$ 31.36
Vested	$ 31.05
Remaining Contractual Life
Outstanding	6 years 6 months
Vested	5 years
Aggregate Intrinsic Value
Outstanding	$ 4,833
Vested	$ 4,819

Share-based compensation arrangement by share-based payment award, options, aggregate intrinsic value.

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- Definition

Share-based compensation arrangement by share-based payment award options outstanding weighted average exercise price.

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Share based compensation arrangement by share based payment award options vested aggregate intrinsic value.

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- Definition

Share based compensation arrangement by share based payment award options vested weighted average exercise Price.

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- Definition

Share based compensation arrangement by share based payment award options vested weighted average remaining contractual life.

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- Definition

Share-based compensation arrangement by share-based payment award, options, weighted average remaining contractual term.

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No definition available.

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- Definition

Share based compensation options outstanding and related information.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Number of options vested.

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