Pensions and Other Postretirement Benefits - Additional Information (Detail) In Millions	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
Sep. 30, 2011 United States Pension Plans of US Entity, Defined Benefit [Member] USD ($)	Sep. 30, 2011 Pension Benefits UK Plans [Member] USD ($)	Sep. 30, 2011 Pension Benefits UK Plans [Member] USD ($)	Sep. 30, 2011 United Kingdom, Pounds GBP (£)	Sep. 30, 2011 United Kingdom, Pounds GBP (£)
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit plan	$ 0	$ 1.2	$ 3.6	£ 0.7	£ 2.2

The increase in the fair value of plan assets from contributions made by the employer.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration