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Segment Information (Details Textual) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Sales Revenue, Services, Net | $ 373,501 | [1] | $ 373,502 | $ 356,185 | $ 300,129 | $ 343,660 | [1] | $ 283,259 | $ 261,934 | $ 253,634 | $ 1,403,317 | $ 1,142,487 | $ 1,061,681
Assets | 603,788 |  |  |  |  | 573,495 |  |  |  |  | 603,788 | 573,495 |
Canadian Operation [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Assets | $ 40,000 |  |  |  |  | $ 45,500 |  |  |  |  | 40,000 | 45,500 |
CANADA |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Sales Revenue, Services, Net |  |  |  |  |  |  |  |  |  |  | 84,100 | 36,500 | 1,500
TD [Member] | CANADA |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Sales Revenue, Services, Net |  |  |  |  |  |  |  |  |  |  | 18,700 | 26,900 | 1,400
CI [Member] | CANADA |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Sales Revenue, Services, Net |  |  |  |  |  |  |  |  |  |  | $ 65,400 | $ 9,600 | $ 100
[1] | Results for the fourth quarter of 2017 include a net Tax Act benefit of $7.8 million, or $0.48 and $0.47 per basic and diluted share, respectively. See further discussion in Note 10 — Income Taxes to our Financial Statements.

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