Employee Benefit Plans - Information Concerning Defined Benefit Pension Plans (Including Certain Plans for Which ABO Exceeds Fair Value of Plan Assets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
PBO for plans for which ABO exceeds plan assets	$ 44,709	$ 44,967
ABO for plans for which ABO exceeds plan assets	44,709	44,967
Fair value of plan assets for plans for which ABO exceeds plan assets	32,360	31,937
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
PBO	53,978	54,261	$ 57,086
Fair value of plan assets	44,222	42,268	$ 44,067
U.S. \| Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
PBO	44,709	44,967
Fair value of plan assets	32,360	31,937
U.K. \| Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
PBO	9,269	9,294
Fair value of plan assets	$ 11,862	$ 10,331

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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=82843861&loc=d3e1928-114920

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ 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=82843861&loc=d3e1928-114920

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- Definition

Amount of accumulated benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess 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 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

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- Definition

Fair value of plan assets for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921

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