Investments In Securities And Interest Rate Swap And Cap Contracts (Schedule Of Notional Amount And Fair Value Of Derivatives) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Derivatives, Fair Value [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (160,402)	[1]	$ (38,915)	[1]	$ (9,718)	[1]
Interest Rate Cap Contracts [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	700,000		700,000
Fair Value	5,966		30,984
Interest Rate Swap Contracts [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Notional Amount			2,140,000
Fair Value			9,113
Interest Rate Swap Contracts [Member] | Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	4,740,000		1,550,000
Fair Value	$ (79,476)		$ (9,757)

[1] See note 2 for additional information on the Company's purpose for entering into interest rate swaps and caps and the decision not to designate them as hedging instruments.