Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity (Schedule Of Repurchase Arrangements And Similar Borrowings) (Details) (USD $) In Thousands, unless otherwise specified													12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Agency Securities [Member]	Dec. 31, 2010 Agency Securities [Member]	Dec. 31, 2011 Year-End Rates Adjusted For Effects Of Related Derivatives Held As Cash Flow Hedges [Member]	Dec. 31, 2010 Year-End Rates Adjusted For Effects Of Related Derivatives Held As Cash Flow Hedges [Member]	Dec. 31, 2011 Borrowings With Maturities Of 30 Days Or Less [Member] Agency Securities [Member]	Dec. 31, 2010 Borrowings With Maturities Of 30 Days Or Less [Member] Agency Securities [Member]	Dec. 31, 2011 Borrowings With Maturities Of 31 To 90 Days [Member] Agency Securities [Member]	Dec. 31, 2010 Borrowings With Maturities Of 31 To 90 Days [Member] Agency Securities [Member]	Dec. 31, 2011 Collateral For Structured Financings [Member]	Dec. 31, 2010 Collateral For Structured Financings [Member]
Repurchase Arrangements And Similar Borrowings, Including Interest Rate Hedging Activity [Line Items]
Secured Debt Outstanding	$ 11,352,444		$ 7,792,743						$ 10,754,835	$ 7,554,225	$ 594,283	$ 235,000
Secured Debt Outstanding													$ 3,326	$ 3,518
Unsecured borrowings, Average Rate	8.49%	[1]	8.49%	8.49%	0.37%	0.31%	0.58%	0.63%	0.37%	0.30%	0.32%	0.33%	8.04%	7.97%

[1] After considering cash flow hedges that coincide with the floating rate terms of these borrowings that begin in 2015 and 2016, the effective borrowing rate during the final 20 years of these borrowings will average 7.56%, subject to certain adjustments for the effects of measured hedge ineffectiveness, if any.