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Acquisitions (Schedule of Allocation of the Purchase Price Consideration of the Fair Value of Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Feb. 22, 2017 | Dec. 31, 2016 | Oct. 11, 2016 | Dec. 31, 2015 | Jun. 09, 2015
--- | --- | --- | --- | --- | --- | ---
Business Acquisition [Line Items] |  |  |  |  |  |
Goodwill | $ 321,074 |  | $ 304,032 |  | $ 292,390 |
Package Concierge |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Cash |  | $ 590 |  |  |  |
Working capital |  | (1,998) |  |  |  |
Property, plant, and equipment |  | 55 |  |  |  |
Acquired intangible assets |  | 3,600 |  |  |  |
Other assets |  | 8 |  |  |  |
Deferred income taxes |  | (128) |  |  |  |
Goodwill |  | 16,790 |  |  |  |
Fair value of purchase consideration |  | $ 18,917 |  |  |  |
Nexus |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Cash |  |  |  | $ 2,495 |  |
Working capital |  |  |  | (1,109) |  |
Property, plant, and equipment |  |  |  | 4,702 |  |
Acquired intangible assets |  |  |  | 6,200 |  |
Other assets |  |  |  | 23 |  |
Goodwill |  |  |  | 11,451 |  |
Fair value of purchase consideration |  |  |  | $ 23,762 |  |
Rough Brothers Incorporated |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |
Cash |  |  |  |  |  | $ 4,651
Working capital |  |  |  |  |  | 21,436
Property, plant, and equipment |  |  |  |  |  | 12,797
Acquired intangible assets |  |  |  |  |  | 56,392
Other assets |  |  |  |  |  | 3,049
Deferred income taxes |  |  |  |  |  | (4,892)
Other liabilities |  |  |  |  |  | (3,028)
Goodwill |  |  |  |  |  | 57,180
Fair value of purchase consideration |  |  |  |  |  | $ 147,585

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