Summary of RSU and Performance Stock Unit Activity (Parenthetical) (Detail) - Restricted Stock Units (RSUs)	Sep. 30, 2018
Awards Granted to Non-Executive Level Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeiture rates	8.00%
Awards Granted to Executive Level Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeiture rates	3.00%

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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