Retirement Plans - Schedule of Accumulated Benefit Obligation in Excess of Plan Assets (Details) - United Kingdom Subsidiary - UK Plan $ in Thousands	Dec. 31, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 383,142
Accumulated benefit obligation	383,142
Fair value of plan assets	$ 347,411

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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Amount of plan asset for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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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/2009/role/commonPracticeRef
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