Pensions and Other Postretirement Benefits - Additional Information (Detail)	3 Months Ended
Mar. 31, 2013 Pension Benefits, U.S. Plans USD ($)	Mar. 31, 2013 Foreign Pension Plans, Defined Benefit [Member] USD ($)	Mar. 31, 2013 Foreign Pension Plans, Defined Benefit [Member] GBP (£)
Pension and Other Postretirement Benefits Disclosure [Line Items]
Description of Defined Contribution Pension and Other Postretirement Plans	We have no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2013
Pension Contributions	$ 0	$ 1,000,000	£ 600,000

Description of and general information regarding the types of plans utilized by the employer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

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-Section 50

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

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-Name Statement of Financial Accounting Standard (FAS)

-Number 158

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2417-114920

+ Details