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Summary of Significant Accounting Policies (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
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Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenue from contracts with customers |  |  |  |  |  |  |  |  | $ 36,806 | $ 40,065 | $ 37,637
Add: non-ASC 606 rental revenue |  |  |  |  |  |  |  |  | 28,672 | 27,628 | 34,017
Total revenue | $ 16,160 | $ 16,396 | $ 18,204 | $ 14,718 | $ 16,660 | $ 15,913 | $ 16,218 | $ 18,902 | 65,478 | 67,693 | 71,654
Compressor - sales |  |  |  |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenue from contracts with customers |  |  |  |  |  |  |  |  | 10,994 | 13,382 | 10,038
Flares - sales |  |  |  |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenue from contracts with customers |  |  |  |  |  |  |  |  | 2,535 | 2,755 | 1,183
Other (Parts/Rebuilds) - sales |  |  |  |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenue from contracts with customers |  |  |  |  |  |  |  |  | 2,740 | 4,071 | 2,400
Service and maintenance |  |  |  |  |  |  |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenue from contracts with customers |  |  |  |  |  |  |  |  | $ 20,537 | $ 19,857 | $ 24,016

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