Convertible Debt (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended				3 Months Ended
	Oct. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Convertible senior notes	Sep. 30, 2014 Convertible senior notes	Dec. 31, 2013 Convertible senior notes
Trading days to calculate settlement									40
Debt Conversion	$ 160,800,000			$ 61,100,000
Debt Instrument, Face Amount								400,000,000		338,900,000	400,000,000
Repayments of Convertible Debt					61,125,000	0
Issuance of Common Stock in connection with conversion of convertible senior notes (in shares)				521,876
Gains (Losses) on Extinguishment of Debt		0	0		(10,787,000)	0
Stock Issued During Period, Shares, Acquisitions				521,876
Payments for Repurchase of Warrants				143,041,000	143,041,000	0
Maximum number of shares issuable upon exercise of warrants				4,033,324			4,760,840
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments					$ 156,657,000