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Goodwill and Intangible Assets - Summary of Goodwill by Reporting Unit (Detail) $ in Thousands | 6 Months Ended
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Jun. 30, 2018 USD ($)
Goodwill [Line Items] |
Beginning balance | $ 1,799
Increases/(decreases) | 84,057
Ending balance | 85,856
Reportable Subsegments [Member] | European Business Segment [Member] |
Goodwill [Line Items] |
Increases/(decreases) | 84,057
Ending balance | 84,057
Reportable Subsegments [Member] | U.S. Business segment [Member] |
Goodwill [Line Items] |
Beginning balance | 1,799
Ending balance | $ 1,799

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