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Retirement Plans - Schedule of Weighted Average Assets Allocation and Weighted Average Target Allocation (Details) - United Kingdom Subsidiary - UK Plan	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocation	100.00%
Asset Allocation	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocation	15.00%
Asset Allocation	14.10%	44.90%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocation	65.00%
Asset Allocation	77.30%	55.00%
Cash
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocation	10.00%
Asset Allocation	8.60%	0.10%
Property
Defined Benefit Plan Disclosure [Line Items]
Target Asset Allocation	10.00%
Asset Allocation	0.00%	0.00%

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ 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 (d)(5)(i)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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