Debt - Notes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Debt Instrument [Roll Forward]
Amortization of debt issuance costs			$ 74	$ 895
Change in fair value of embedded derivative	$ 1,235	$ (16,556)	(188)	$ (66,344)
Notes
Debt Instrument [Roll Forward]
Embedded conversion option, beginning balance			23,737
2033 Senior Notes, beginning balance			32,200
Discount, beginning balance			(6,525)
Debt issuance cost, beginning balance			(426)
Total, beginning balance			48,986
Amortization of debt discount			907
Amortization of debt issuance costs			74
Amortization of debt discount and debt issuance costs			981
Change in fair value of embedded derivative			(4,734)
Embedded conversion option, ending balance	19,003		19,003
2033 Senior Notes, ending balance	32,200		32,200
Discount, ending balance	(5,618)		(5,618)
Debt issuance cost, ending balance	(352)		(352)
Total, ending balance	$ 45,233		$ 45,233