Stock-Based Compensation - Employee Withholding Taxes on Stock Awards - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Employee Withholding Taxes on Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment of withholding taxes related to stock awards	$ 0.4	$ 1.0

Amount of cash outflow to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration