Derivatives (Details 3) (Discounted Cash Flow [Member], Level 3 Fair Value Measurements [Member], Series F Agreement [Member], USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
Quantitative information about Level 3 fair value measurements
Fair Value of Liabilities	(1,433)
Maximum [Member]
Quantitative information about Level 3 fair value measurements
Fair value inputs, long dated treasuries	2.88%
Fair value inputs, own credit risk	2.78%
Minimum [Member]
Quantitative information about Level 3 fair value measurements
Fair value inputs, long dated treasuries	2.72%
Fair value inputs, own credit risk	1.55%