Notes Payable, Long-Term Debt and Other Obligations (Other Schedules) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	$ 4,053	$ 18,512	$ 55,769
Fair Value Of Derivatives [Roll Forward]
Loss (gain) from changes in fair value of embedded derivatives	(4,999)	(26,425)	(44,989)
Unamortized Debt Discount Reconciliation [Roll Forward]
Amortization of beneficial conversion feature	(1,223)	(6,301)	(30,854)
Variable Interest Senior Convertible Debt
Unamortized Debt Discount Reconciliation [Roll Forward]
Beginning balance of unamortized discount	5,276	32,824	122,940
Amortization of embedded derivatives	(4,053)	(18,512)	(55,769)
Amortization of beneficial conversion feature	(1,223)	(6,301)	(30,854)
Ending balance of unamortized discount	0	5,276	32,824
Variable Interest Senior Convertible Debt | Embedded Derivatives
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	4,999	31,424	76,413
Loss (gain) from changes in fair value of embedded derivatives	(4,999)	(26,425)	(44,989)
Beginning balance of derivative liability fair value	0	4,999	31,424
Variable Interest Senior Convertible Debt | 7.5% Variable Interest Senior Convertible Notes due 2019
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	0	2,031	39,845
Fair Value Of Derivatives [Roll Forward]
Loss (gain) from changes in fair value of embedded derivatives	0	(6,635)	(24,530)
Unamortized Debt Discount Reconciliation [Roll Forward]
Beginning balance of unamortized discount	0	3,359	69,253
Amortization of embedded derivatives	0	(2,031)	(39,845)
Amortization of beneficial conversion feature	0	(1,328)	(26,049)
Ending balance of unamortized discount	0	0	3,359
Variable Interest Senior Convertible Debt | 7.5% Variable Interest Senior Convertible Notes due 2019 | Embedded Derivatives
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	0	6,635	31,165
Loss (gain) from changes in fair value of embedded derivatives	0	(6,635)	(24,530)
Beginning balance of derivative liability fair value	0	0	6,635
Variable Interest Senior Convertible Debt | 5.5% Variable Interest Senior Convertible Notes due 2020
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	4,053	16,481	15,924
Fair Value Of Derivatives [Roll Forward]
Loss (gain) from changes in fair value of embedded derivatives	(4,999)	(19,790)	(20,459)
Unamortized Debt Discount Reconciliation [Roll Forward]
Beginning balance of unamortized discount	5,276	29,465	53,687
Amortization of embedded derivatives	(4,053)	(16,481)	(15,924)
Amortization of beneficial conversion feature	(1,223)	(4,973)	(4,805)
Ending balance of unamortized discount	0	5,276	29,465
Variable Interest Senior Convertible Debt | 5.5% Variable Interest Senior Convertible Notes due 2020 | Interest Rate Risk
Unamortized Debt Discount Reconciliation [Roll Forward]
Partial redemption of 5.5% convertible notes		(2,735)	(3,493)
Variable Interest Senior Convertible Debt | 5.5% Variable Interest Senior Convertible Notes due 2020 | Embedded Derivatives
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	4,999	24,789	45,248
Loss (gain) from changes in fair value of embedded derivatives	(4,999)	(19,790)	(20,459)
Beginning balance of derivative liability fair value	$ 0	$ 4,999	$ 24,789