Fair Value Measurements (Narrative) (Details)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Inputs, Prepayment Rate	1.00%	1.00%
Payment at maturity, percent	100.00%	100.00%
Basis points	150	150
Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Collateral discount	30.00%	30.00%
Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Collateral discount	20.00%	20.00%