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Concentrations of Credit Risk and Major Customers (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) Customer | Dec. 31, 2017 USD ($) Customer | Dec. 31, 2016
Concentration Risk |  |  |
Concentration of risk, number of customers | 5 |  |
Concentration Risk, Percentage | 37.00% | 38.00% | 40.00%
Sales Revenue, Services, Net [Member] | Customer Concentration Risk [Member] |  |  |
Concentration Risk |  |  |
Concentration of risk, number of customers | 1 | 1 |
Concentration Risk, Percentage | 12.50% | 12.60% | 12.30%
Baseline percentage for customer concentration of risk | 10.00% | 10.00% |
Accounts Receivable [Member] | Customer Concentration Risk [Member] |  |  |
Concentration Risk |  |  |
Accounts receivable | $ | $ 6.7 | $ 7.5 |
Concentration Risk, Percentage | 36.00% | 32.00% |

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