Summary of Significant Accounting Policies (Fair Value of Derivatives Embedded within Convertible Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Embedded Derivative [Line Items]
Fair value of derivatives embedded within convertible debt	$ 4,999	$ 31,424
Minimum
Embedded Derivative [Line Items]
Fair value of derivatives embedded within convertible debt	4,993	31,371
Maximum
Embedded Derivative [Line Items]
Fair value of derivatives embedded within convertible debt	$ 5,005	$ 31,519