Pension and Other Postretirement Benefits - Schedule of Net Funded Status of the Plans (Detail) In Thousands, unless otherwise specified	Dec. 31, 2014 USD ($)	Dec. 31, 2014 U.S. Pension Benefits [Member] USD ($)	Dec. 31, 2013 U.S. Pension Benefits [Member] USD ($)	Dec. 31, 2012 U.S. Pension Benefits [Member] USD ($)	Dec. 31, 2014 Foreign Pension Benefits [Member] USD ($)	Dec. 31, 2014 Foreign Pension Benefits [Member] GBP (£)	Dec. 31, 2013 Foreign Pension Benefits [Member] USD ($)	Dec. 31, 2013 Foreign Pension Benefits [Member] GBP (£)	Dec. 31, 2012 Foreign Pension Benefits [Member] USD ($)	Dec. 31, 2014 Other Postretirement Benefits [Member] USD ($)	Dec. 31, 2013 Other Postretirement Benefits [Member] USD ($)	Dec. 31, 2012 Other Postretirement Benefits [Member] USD ($)
Funded status of the plans:
Fair value of plan assets	$ 157,048	$ 157,048	$ 164,085	$ 140,218	$ 50,533	£ 32,437	$ 48,536	£ 29,315	$ 41,875	$ 0	$ 0	$ 0
Less benefit obligations		205,399	181,606	197,057	70,523		60,830		59,210	13,739	20,129	22,806
Funded status at December 31	$ (39,000)	$ (48,351)	$ (17,521)		$ (19,990)		$ (12,294)			$ (13,739)	$ (20,129)

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Projected Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6522206

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Postretirement Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503904

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 35

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=29635418&loc=d3e12355-114930

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- Definition

The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919

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