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Acquisitions (Narrative) (Details) - USD ($) $ in Thousands | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2017 | Feb. 22, 2017 | Oct. 11, 2016
--- | --- | --- | --- | --- | ---
Business Acquisition [Line Items] |  |  |  |  |
Goodwill |  | $ 304,032 | $ 321,093 |  |
Package Concierge |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Aggregate consideration for acquisition | $ 18,917 |  |  |  |
Goodwill |  |  |  | $ 16,863 |
Nexus Corporation |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Aggregate consideration for acquisition |  | 23,762 |  |  |
Goodwill |  |  |  |  | $ 11,451
Working capital adjustment payable |  | $ 1,000 | $ 167 |  |

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