Financing (Details 8) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Unrealized Gain Loss On Hybrid Instrument Gross	$ 37,620	$ (15,899)	$ 6,450	$ (13,428)
Less: Day-one loss from debenture financings	(847)		(847)
Change in fair value of hybrid financial instruments	36,773	(15,899)	5,603	(13,428)
Debentures 2007 Series [Member]
Change in fair value of hybrid financial instruments	24,068	(12,052)	(989)	(10,032)
Debentures 2008 Series [Member]
Change in fair value of hybrid financial instruments	9,663	(3,847)	3,550	(3,396)
Debentures 2006 Series [Member]
Change in fair value of hybrid financial instruments	1,734	0	1,734	0
Debentures 2009 Series [Member]
Change in fair value of hybrid financial instruments	433	0	433	0
Debentures 2010 Series [Member]
Change in fair value of hybrid financial instruments	896	0	896	0
Debentures 2011 Series [Member]
Change in fair value of hybrid financial instruments	512	0	512	0
Debentures 2012 Series [Member]
Change in fair value of hybrid financial instruments	$ 314	$ 0	$ 314	$ 0