Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands  | 
1 Months Ended | 3 Months Ended | 9 Months Ended | |||||
|---|---|---|---|---|---|---|---|---|
Sep. 30, 2019  | 
Aug. 31, 2018  | 
Jun. 30, 2018  | 
Apr. 30, 2018  | 
Sep. 30, 2019  | 
Sep. 30, 2018  | 
Sep. 30, 2019  | 
Sep. 30, 2018  | 
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| Realized and Unrealized Gains (Losses) on Financial Instruments | ||||||||
| Realized and unrealized gains (losses) on financial instruments, net | $ (433) | $ 5,678 | $ (433) | $ 3,659 | ||||
| Series C common stock | Zero-strike call option | ||||||||
| Realized and Unrealized Gains (Losses) on Financial Instruments | ||||||||
| Realized and unrealized gains (losses) on financial instruments, net | $ (433) | $ 5,678 | $ (433) | $ 3,659 | ||||
| Derivative underlying share amount | 460,675 | 621,920 | 632,911 | 610,325 | 460,675 | 460,675 | ||
| Derivative premium paid | $ 46,300 | $ 48,600 | $ 47,800 | |||||
| Derivative settlement proceeds | $ 46,500 | |||||||
| X | ||||||||||
- Definition Derivative premium paid No definition available. 
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- Definition Derivative settlement proceeds No definition available. 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount of realized and unrealized gain (loss) on investment. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition The number of issuer's shares to which the option contract is indexed. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Details 
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- Details 
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