Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements. (Details)

v3.21.1
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