Equity-Based Compensation Summary of Number of Share-Based Awards Granted (Detail)	6 Months Ended
Jun. 30, 2017 $ / shares shares
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based awards granted \| shares	33,907
Grant-date fair value of awards per share \| $ / shares	$ 58.58
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based awards granted \| shares	66,774
Grant-date fair value of awards per share \| $ / shares	$ 56.45
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant-date fair value of awards per share \| $ / shares	$ 18.82
Options, Grants in Period, Gross \| shares	158,484

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).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted average fair value at grant date for nonvested equity-based awards issued 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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Gross number of share options (or share units) granted during the period.

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