Stock-Based Compensation - Fair Value of Options (Parenthetical) (Detail)	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price volatility, risk free interest period	5 years	5 years

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.

No definition available.

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