Notes Payable, Long-Term Debt and Other Obligations (Other Schedules) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	$ 55,769	$ 37,210	$ 25,732
Fair Value Of Derivatives [Roll Forward]
Loss (gain) from changes in fair value of embedded derivatives	(44,989)	(35,919)	(31,710)
Unamortized Debt Discount Reconciliation [Roll Forward]
Amortization of beneficial conversion feature	(30,854)	(19,577)	(12,796)
Variable Interest Senior Convertible Debt
Unamortized Debt Discount Reconciliation [Roll Forward]
Beginning balance of unamortized discount	122,940	179,727	218,255
Amortization of embedded derivatives	(55,769)	(37,210)	(25,732)
Amortization of beneficial conversion feature	(30,854)	(19,577)	(12,796)
Ending balance of unamortized discount	32,824	122,940	179,727
Variable Interest Senior Convertible Debt | Embedded Derivatives
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	76,413	112,332	144,042
Loss (gain) from changes in fair value of embedded derivatives	(44,989)	(35,919)	(31,710)
Beginning balance of derivative liability fair value	31,424	76,413	112,332
Variable Interest Senior Convertible Debt | 7.5% Variable Interest Senior Convertible Notes due 2019
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	39,845	23,720	14,294
Fair Value Of Derivatives [Roll Forward]
Loss (gain) from changes in fair value of embedded derivatives	(24,530)	(21,734)	(19,184)
Unamortized Debt Discount Reconciliation [Roll Forward]
Beginning balance of unamortized discount	69,253	108,480	132,119
Amortization of embedded derivatives	(39,845)	(23,720)	(14,294)
Amortization of beneficial conversion feature	(26,049)	(15,507)	(9,345)
Ending balance of unamortized discount	3,359	69,253	108,480
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	31,165	52,899	72,083
Loss (gain) from changes in fair value of embedded derivatives	(24,530)	(21,734)	(19,184)
Beginning balance of derivative liability fair value	6,635	31,165	52,899
Variable Interest Senior Convertible Debt | 5.5% Variable Interest Senior Convertible Notes due 2020
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	15,924	13,490	11,438
Fair Value Of Derivatives [Roll Forward]
Loss (gain) from changes in fair value of embedded derivatives	(20,459)	(14,185)	(12,526)
Unamortized Debt Discount Reconciliation [Roll Forward]
Beginning balance of unamortized discount	53,687	71,247	86,136
Amortization of embedded derivatives	(15,924)	(13,490)	(11,438)
Amortization of beneficial conversion feature	(4,805)	(4,070)	(3,451)
Ending balance of unamortized discount	29,465	53,687	71,247
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	(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	45,248	59,433	71,959
Loss (gain) from changes in fair value of embedded derivatives	(20,459)	(14,185)	(12,526)
Beginning balance of derivative liability fair value	$ 24,789	$ 45,248	$ 59,433