Trade Inventory (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2018 |
Dec. 31, 2017 |
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| Trade Inventory [Abstract] | ||
| Inventory writedowns included in costs of goods sold | $ 0.0 | $ 0.4 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Nonrecurring impairment charges related to the write-off of production-related equipment and inventory. This tag is used when an Entity charges this cost to cost of goods sold. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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