Contingencies And Other Disclosures (Schedule Of Original Purchase Amount Of Investments Subject To Litigation) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Alternativea Mortgage Loan Pools [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	$ 1,325,855
Alternativea Mortgage Loan Pools [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	0
Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2005 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	843,868	[1]
Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2005 [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	0
Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2006 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	277,926	[1]
Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2006 [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	0
Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2007 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	204,061
Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2007 [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	0
Jumbo Mortgage Loans [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	164,659
Jumbo Mortgage Loans [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	16,877
Jumbo Mortgage Loans [Member] | Origination Vintage Period 2005 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	30,000
Jumbo Mortgage Loans [Member] | Origination Vintage Period 2005 [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	0
Jumbo Mortgage Loans [Member] | Origination Vintage Period 2006 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	84,659
Jumbo Mortgage Loans [Member] | Origination Vintage Period 2006 [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	9,793
Jumbo Mortgage Loans [Member] | Origination Vintage Period 2007 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	50,000
Jumbo Mortgage Loans [Member] | Origination Vintage Period 2007 [Member] | Junior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	7,084
Federal Housing Finance Agency [Member] | Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2005 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	643,751
Federal Housing Finance Agency [Member] | Alternativea Mortgage Loan Pools [Member] | Origination Vintage Period 2006 [Member] | Senior Investor Rank [Member]
Loss Contingencies [Line Items]
Original purchase amounts of the investments at issue	$ 230,020

[1] The amounts shown in the table which are the subject of the FHFA litigations include $230,020 of the Senior Alt-A loans from 2006 and $643,751 of the Senior Alt-A from 2005.