Stockholders' Equity Common Stock - Employee Stock Purchase Plan - Additional Information (Detail) - Employee Stock Purchase Plan [Member]	3 Months Ended
Mar. 31, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of eligible earning contributed toward semi-annual purchase of common stock	15.00%
Offering period under the plan	6 months
Percentage of purchase price with respect to each offering period	85.00%
Aggregate shares of common stock reserved for issuance	1,900,000
Shares issued under ESPP	400,000
Percentage of common stock shares outstanding	1.00%

Offering period under the plan.

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Percentage common stock outstanding shares.

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- Definition

Percentage of purchase price with respect to each offering period.

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- Definition

Number of common shares reserved for future issuance related to deferred compensation arrangements with individuals.

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- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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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.

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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