Weighted-Average Fair Value of Performance Stock Units (Parenthetical) (Detail) - Performance Shares	9 Months Ended
Sep. 30, 2015 $ / shares
$50 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum average market closing price to earn PSU	$ 50.00
$60 Vesting Hurdle
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum average market closing price to earn PSU	$ 60.00

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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