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Stock-Based Compensation - Summary of RSU and PSA Activity (Detail) - Restricted Stock Units (RSU) and Performance Share Awards (PSAs) [Member] - shares	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance	888,942	1,001,814
Granted	152,531	167,255
Forfeited	(77,652)	(38,458)
Shares delivered	(283,627)	(239,394)
Ending Balance	680,194	891,217

X

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ 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)(1)(iv)(3)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

X

- 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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X

- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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)(i)-(ii)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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X

- Definition

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.

+ References

No definition available.

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X

- Definition

Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef



-Publisher FASB



-Name Accounting Standards Codification



-Topic 505



-SubTopic 10



-Section 50



-Paragraph 2



-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644



Reference 2: http://www.xbrl.org/2003/role/presentationRef



-Publisher FASB



-Name Accounting Standards Codification



-Topic 505



-SubTopic 10



-Section S99



-Paragraph 1



-Subparagraph (SX 210.3-04)



-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770



Reference 3: http://www.xbrl.org/2003/role/presentationRef



-Publisher SEC



-Name Regulation S-X (SX)



-Number 210



-Section 02



-Paragraph 29, 30



-Article 5

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