Transactions with Related Parties (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Related Party Transaction [Line Items]
Net gains (losses) on derivatives and hedging activities	$ 3,482,000	$ (5,285,000)	$ 2,641,000	$ (5,178,000)
Principal Owner [Member]
Related Party Transaction [Line Items]
Contractual Interest Income, Federal Home Loan Bank Advances	87,300,000	128,900,000	329,800,000	393,800,000
Net gains (losses) on derivatives and hedging activities	(55,600,000)	(94,300,000)	(215,300,000)	(287,000,000)
Interest Income, Federal Home Loan Bank Advances, Amortization Of Basis Adjustments	$ (1,100,000)	$ (8,800,000)	$ (14,100,000)	$ (26,300,000)