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Discontinued Operations - Summary of Non-Cash Adjustments Related to Discontinued Operations (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018 | Dec. 31, 2017
Discontinued Operations And Disposal Groups [Abstract] |  |  |  |
Depreciation and amortization | $ 344 | $ 393 | $ 1,625 | $ 1,630
Provision for excess inventory | $ 0 | 326 | 463 | 340
(Loss) gain on asset disposal |  | $ 22 | $ (36) | $ 40

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- Definition Amount of deprecation and amortization expense attributable to property, plant and equipment and intangible assets of discontinued operations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760 + Details
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