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Retirement Plans - Schedule of Accumulated Benefit Obligation in Excess of Fair Value of Plan Assets (Details) - United Kingdom Subsidiary - UK Plan - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
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Defined Benefit Plan Disclosure [Line Items] |  |
Projected benefit obligation | $ 295,825 | $ 332,806
Accumulated benefit obligation | 295,825 | 332,806
Fair value of plan assets | $ 263,555 | $ 282,095

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