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Acquisitions (Narrative) (Details) - USD ($) $ in Thousands |  |  | 3 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2016 | Jun. 09, 2015 | Dec. 31, 2016 | Dec. 31, 2017 | Oct. 11, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Business Acquisition [Line Items] |  |  |  |  |  |  |
Remaining purchase adjustment | $ 2,314 |  | $ 2,314 |  |  |  |
Goodwill | 304,032 |  | 304,032 |  |  | $ 292,390 | $ 236,044
Nexus |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Acquisition purchase price | $ 24,594 |  |  |  |  |  |
Working capital adjustment |  |  | $ 93 |  |  |  |
Goodwill |  |  |  |  | $ 12,283 |  |
Fair value of purchase consideration |  |  |  |  | $ 24,594 |  |
Nexus | Forecast |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Purchase adjustment to be paid |  |  |  | $ 1,000 |  |  |
Rough Brothers Incorporated |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Acquisition purchase price |  | $ 147,585 |  |  |  |  |
Working capital adjustment |  | 6,302 |  |  |  |  |
Goodwill |  | 57,180 |  |  |  |  |
Tax deductible goodwill |  | 37,969 |  |  |  |  |
Indemnification assets |  | 3,000 |  |  |  |  |
Fair value of purchase consideration |  | $ 147,585 |  |  |  |  |

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