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Basis of Presentation and Summary of Significant Accounting Policies (Contract Balances) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018
Accounts Receivable |  |
Accounts receivable - contracts with customers | $ 3,484 | $ 2,250
Accounts receivable - non-ASC 606 | 7,113 | 5,260
Total Accounts Receivable | 10,597 | 7,510
Less: Allowance for doubtful accounts | (299) | (291)
Total Accounts Receivable, net | 10,298 | 7,219
Deferred income | 133 | 81
Revenue recognized | $ 15 | $ 176

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