Fair Value Measurements. (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Fair Value Measurements. (Details) [Line Items] | |||
| Property and equipment held-for-sale at fair value | $ 48,548,000 | $ 70,400,000 | |
| Issued pre-funded warrants | $ 0.001 | ||
| Exercise price | 9.76 | $ 1.00 | |
| Pre-funded Warrants and Other Warrants [Member] | |||
| Fair Value Measurements. (Details) [Line Items] | |||
| Exercise price | $ 9.757 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Issued pre-funded warrants. No definition available.
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| X | ||||||||||
- Definition Fair value portion of assets classified as held for sale. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Exercise price per share or per unit of warrants or rights outstanding. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Details
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