Financing (Details 6) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	$ (4,173)	$ 21,809
Less: Day-one loss from debenture financings	0	0
Gain (loss) from changes in fair value of hybrid instruments	(4,173)	21,809
Debentures 2006 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(255)	11,604
Debentures 2007 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(82)	16,381
Debentures 2008 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(220)	13,291
Debentures 2009 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(6)	2,113
Debentures 2010 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	0	7,177
Debentures 2011 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(93)	1,748
Debentures 2012 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(126)	1,321
Debentures 2013 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	(3,412)	(31,826)
Debentures 2014 Series [Member]
Debt Conversion [Line Items]
Unrealized Gain Loss On Hybrid Instrument Gross	$ (8)	$ 0