Quantitative Information About Level 3 Fair Value Measurements - Default Assumptions (Details)	12 Months Ended
	Dec. 31, 2012
[RealEstateOwnedMember]
Default Assumptions [Line Items]
Range Of Loss Timining	Next 10 Months
[LoansInForeclosureMember]
Default Assumptions [Line Items]
Range Of Loss Timining	Month 4 - 13
[Loans90DaysDelinquentMember]
Default Assumptions [Line Items]
Range Of Loss Timining	Month 13 - 30
[Loans60DaysDelinquentMember]
Default Assumptions [Line Items]
Range Of Loss Timining	Month 13 - 30
[Loans30DaysDelinquentMember]
Default Assumptions [Line Items]
Range Of Loss Timining	Month 13 - 30
[CurrentLoansMember]
Default Assumptions [Line Items]
Range Of Loss Timining	Month 31 and Beyond
[RetainedInterestMember] | [RealEstateOwnedMember]
Default Assumptions [Line Items]
Probability of Default	100.00%
[RetainedInterestMember] | [RealEstateOwnedMember] | [MaximumMember]
Default Assumptions [Line Items]
Loss Severity Range	52.23%
[RetainedInterestMember] | [RealEstateOwnedMember] | [MinimumMember]
Default Assumptions [Line Items]
Loss Severity Range	35.20%
[RetainedInterestMember] | [RealEstateOwnedMember] | [WeightedAverageMember]
Default Assumptions [Line Items]
Loss Severity Range	40.29%
[RetainedInterestMember] | [LoansInForeclosureMember]
Default Assumptions [Line Items]
Probability of Default	100.00%
[RetainedInterestMember] | [LoansInForeclosureMember] | [MaximumMember]
Default Assumptions [Line Items]
Loss Severity Range	52.23%
[RetainedInterestMember] | [LoansInForeclosureMember] | [MinimumMember]
Default Assumptions [Line Items]
Loss Severity Range	35.20%
[RetainedInterestMember] | [LoansInForeclosureMember] | [WeightedAverageMember]
Default Assumptions [Line Items]
Loss Severity Range	40.29%
[RetainedInterestMember] | [Loans90DaysDelinquentMember]
Default Assumptions [Line Items]
Probability of Default	100.00%
[RetainedInterestMember] | [Loans90DaysDelinquentMember] | [MaximumMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans90DaysDelinquentMember] | [MinimumMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans90DaysDelinquentMember] | [WeightedAverageMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans60DaysDelinquentMember]
Default Assumptions [Line Items]
Probability of Default	85.00%
[RetainedInterestMember] | [Loans60DaysDelinquentMember] | [MaximumMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans60DaysDelinquentMember] | [MinimumMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans60DaysDelinquentMember] | [WeightedAverageMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans30DaysDelinquentMember]
Default Assumptions [Line Items]
Probability of Default	75.00%
[RetainedInterestMember] | [Loans30DaysDelinquentMember] | [MaximumMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans30DaysDelinquentMember] | [MinimumMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [Loans30DaysDelinquentMember] | [WeightedAverageMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%
[RetainedInterestMember] | [CurrentLoansMember] | [MaximumMember]
Default Assumptions [Line Items]
Probability of Default	4.40%
Loss Severity Range	45.00%
[RetainedInterestMember] | [CurrentLoansMember] | [MinimumMember]
Default Assumptions [Line Items]
Probability of Default	2.50%
Loss Severity Range	45.00%
[RetainedInterestMember] | [CurrentLoansMember] | [WeightedAverageMember]
Default Assumptions [Line Items]
Loss Severity Range	45.00%