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Acquisitions (Narrative) (Details) - USD ($) $ in Thousands | Aug. 30, 2019 | Aug. 21, 2018 | Sep. 30, 2019 | Dec. 31, 2018
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Business Acquisition [Line Items] |  |  |  |
Goodwill |  |  | $ 327,983 | $ 323,671
Apeks |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Aggregate consideration for acquisition | $ 12,600 |  |  |
Goodwill | $ 4,185 |  |  |
SolarBOS |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Aggregate consideration for acquisition |  | $ 6,400 |  |
Goodwill |  | $ 2,879 |  |
Maximum | Apeks |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Working capital adjustment period | 6 months |  |  |
Minimum | Apeks |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Working capital adjustment period | 3 months |  |  |

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