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Description of Business and Summary of Significant Accounting Policies - Description of Business (Details) - subsidiary | Dec. 31, 2017 | Aug. 31, 2015
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Business Acquisition [Line Items] |  |
Number of owned subsidiaries | 2 |
Kelway TopCo Limited |  |
Business Acquisition [Line Items] |  |
Percent of outstanding common stock purchased |  | 65.00%
Non-controlling interest held |  | 35.00%
Total percentage owned, after acquisition |  | 100.00%

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- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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