Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Cash in lieu of return on pledged collateral received	$ 8,300,000
Loss on sale of bonds	62,000
Swap agreements average expiration period (in months)	15
Notional amount of swap agreement		100,000,000
Average fixed rates of interest rate swap agreements		4.09%
Term of LIBOR interest rate agreement (years)	20	20
Derivatives held as cash flow hedges	30,200,000	6,500,000
Minimum [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Maturity period of repurchase arrangements (days)	30
Maximum [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Maturity period of repurchase arrangements (days)	90
Repurchase Arrangements And Similar Borrowings [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Interest paid on Repurchase arrangements and similar borrowings	55,200,000	56,300,000	135,000,000
Interest Rate Swap [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Swap agreements hedging short-term interest rates	3,000,000,000
Swap [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Notional amount of swap agreement	$ 1,800,000,000