Share-Based Compensation - Summary of Restricted Stock Option Granted (Detail) (Restricted Shares [Member], USD $)	12 Months Ended
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Awards, Granted	507,063
Fair Value per Share at the Grant date	$ 37.30
November 4, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date	2013-11-04
Number of Awards, Granted	400,000
Fair Value per Share at the Grant date	$ 12.38
May 8, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date	2014-05-08
Number of Awards, Granted	100,000
Fair Value per Share at the Grant date	$ 29.00
October 9, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date	2014-10-09
Number of Awards, Granted	406,000
Fair Value per Share at the Grant date	$ 39.35
December 9, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date	2014-12-09
Number of Awards, Granted	1,063
Fair Value per Share at the Grant date	$ 36.71

Share Based Compensation Arrangement By Share Based Payment Award Award Grant Date

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- Definition

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).

+ References

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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- Definition

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).

+ References

+ Details

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