Notes Payable, Long Term Debt and Other Obligations - Other Schedules (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	$ 18,529	$ 32,071	$ 21,482
Unamortized Debt Discount [Roll Forward]
Amortization of beneficial conversion feature	(8,681)	(19,401)	(14,896)
Ending balance of unamortized discount	210,241
Convertible Debt [Member]
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	245,465	201,075	273,323
Decrease in unamortized discount due to conversion			(35,870)
Issuance of convertible notes - embedded derivative		82,775
Increase of convertible notes - beneficial conversion feature		24,974
Amortization of embedded derivatives	(18,529)	(32,071)	(21,482)
Amortization of beneficial conversion feature	(8,681)	(19,401)	(14,896)
Ending balance of unamortized discount	218,255	245,465	201,075
Convertible Debt [Member] | 6.75% Senior Convertible Debentures [Member]
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	0	6,097	5,914
Convertible Debt [Member] | 6.75% Variable Interest Senior Convertible Exchange Notes due 2014 [Member]
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	0	13,570	11,799
Convertible Debt [Member] | 3.875% Senior Convertible Debentures [Member]
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	0	0	155
Convertible Debt [Member] | 7.5% Senior Convertible Debentures [Member]
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	8,777	5,553	3,614
Convertible Debt [Member] | 5.5% Variable Interest Senior Convertible Debentures due 2020 [Member]
Debt Instrument [Line Items]
Interest expense associated with embedded derivatives	9,752	6,851	0
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	98,831
Ending balance of unamortized discount	86,136	98,831
Interest Rate Risk [Member]
Debt Instrument [Line Items]
Gain on changes in fair value of derivatives embedded within convertible debt	24,455	19,409	18,935
Interest Rate Risk [Member] | Convertible Debt [Member]
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	169,386	112,062	172,128
Decrease in derivative due to conversion	(889)		(41,131)
Increase from issuance		82,775
(Gain) loss from changes in fair value of embedded derivatives	(24,455)	(19,409)	(18,935)
Ending balance of derivative liability fair value	144,042	169,386	112,062
Interest Rate Risk [Member] | Convertible Debt [Member] | 6.75% Senior Convertible Debentures [Member]
Debt Instrument [Line Items]
Gain on changes in fair value of derivatives embedded within convertible debt	(5)	3,212	5,075
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	884	6,607	11,682
Decrease in derivative due to conversion	(889)	(2,511)
(Gain) loss from changes in fair value of embedded derivatives	5	(3,212)	(5,075)
Ending balance of derivative liability fair value	0	884	6,607
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	0	19,312	30,383
Decrease in unamortized discount due to conversion		(7,898)
Issuance of convertible notes - embedded derivative		0
Increase of convertible notes - beneficial conversion feature		0
Amortization of embedded derivatives	0	(6,097)	(5,914)
Amortization of beneficial conversion feature	0	(5,317)	(5,157)
Ending balance of unamortized discount	0	0	19,312
Interest Rate Risk [Member] | Convertible Debt [Member] | 6.75% Variable Interest Senior Convertible Exchange Notes due 2014 [Member]
Debt Instrument [Line Items]
Gain on changes in fair value of derivatives embedded within convertible debt	0	8,990	9,625
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	0	12,521	22,146
Decrease in derivative due to conversion		(3,531)
(Gain) loss from changes in fair value of embedded derivatives	0	(8,990)	(9,625)
Ending balance of derivative liability fair value	0	0	12,521
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	0	25,945	45,038
Decrease in unamortized discount due to conversion		(3,989)
Issuance of convertible notes - embedded derivative		0
Increase of convertible notes - beneficial conversion feature		0
Amortization of embedded derivatives	0	(13,570)	(11,799)
Amortization of beneficial conversion feature	0	(8,386)	(7,294)
Ending balance of unamortized discount	0	0	25,945
Interest Rate Risk [Member] | Convertible Debt [Member] | 3.875% Senior Convertible Debentures [Member]
Debt Instrument [Line Items]
Gain on changes in fair value of derivatives embedded within convertible debt	0	0	(1,417)
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	0	0	39,714
Decrease in derivative due to conversion			(41,131)
(Gain) loss from changes in fair value of embedded derivatives	0	0	1,417
Ending balance of derivative liability fair value	0	0	0
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	0	0	36,107
Decrease in unamortized discount due to conversion			(35,870)
Issuance of convertible notes - embedded derivative		0
Increase of convertible notes - beneficial conversion feature		0
Amortization of embedded derivatives	0	0	(155)
Amortization of beneficial conversion feature	0	0	(82)
Ending balance of unamortized discount	0	0	0
Interest Rate Risk [Member] | Convertible Debt [Member] | 7.5% Senior Convertible Debentures [Member]
Debt Instrument [Line Items]
Gain on changes in fair value of derivatives embedded within convertible debt	15,555	5,296	5,652
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	87,638	92,934	98,586
(Gain) loss from changes in fair value of embedded derivatives	(15,555)	(5,296)	(5,652)
Ending balance of derivative liability fair value	72,083	87,638	92,934
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	146,634	155,818	161,795
Issuance of convertible notes - embedded derivative		0
Increase of convertible notes - beneficial conversion feature		0
Amortization of embedded derivatives	(8,777)	(5,553)	(3,614)
Amortization of beneficial conversion feature	(5,738)	(3,631)	(2,363)
Ending balance of unamortized discount	132,119	146,634	155,818
Interest Rate Risk [Member] | Convertible Debt [Member] | 5.5% Variable Interest Senior Convertible Debentures due 2020 [Member]
Debt Instrument [Line Items]
Gain on changes in fair value of derivatives embedded within convertible debt	8,905	1,911	0
Fair Value Of Derivatives [Roll Forward]
Beginning balance of derivative liability fair value	80,864	0	0
Increase from issuance		82,775
(Gain) loss from changes in fair value of embedded derivatives	(8,905)	(1,911)	0
Ending balance of derivative liability fair value	71,959	80,864	0
Unamortized Debt Discount [Roll Forward]
Beginning balance of unamortized discount	98,831	0	0
Issuance of convertible notes - embedded derivative		82,775
Increase of convertible notes - beneficial conversion feature		24,974
Amortization of embedded derivatives	(9,752)	(6,851)	0
Amortization of beneficial conversion feature	(2,943)	(2,067)	0
Ending balance of unamortized discount	$ 86,136	$ 98,831	$ 0