Commitments and Contingencies - Additional Information (Detail) In Millions, unless otherwise specified	Sep. 30, 2013 USD ($)	Sep. 30, 2013 GBP (£)
Commitments And Contingencies Disclosure [Abstract]
Proposed adjustment to payroll tax liability	$ 6.3	£ 3.9

The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

Name:	us-gaap_IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant