Assets and Liabilities Held for Sale - Additional Information (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|
Mar. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Mar. 31, 2019 |
Mar. 31, 2018 |
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| Discontinued Operations And Disposal Groups [Abstract] | |||||
| Impairment loss | $ 6,449 | $ 0 | $ 14,816 | $ 6,449 | $ 14,816 |
| X | ||||||||||
- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- References No definition available.
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