Schedule Of Interest Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]
Coupon interest	$ 114,328	$ 163,964	$ 232,726	$ 331,397
Net premium amortization	(24,870)	(48,849)	(46,961)	(92,041)
Interest income	$ 89,458	$ 115,115	$ 185,765	$ 239,356