Stock-Based Compensation - Additional Information (Detail) - $ / shares	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issuances under equity compensation plans	642,024	1,092,371	5,247,748	3,741,140
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted stock options	190,000	833,290	928,675	2,118,310
Weighted average grant-date fair value	$ 30.52	$ 10.38	$ 39.28	$ 9.36
Restricted Stock Units (RSU) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	152,151	110,500	558,391	110,500

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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-Name Accounting Standards Codification
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-SubTopic 10
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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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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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