Expected Losses to be Paid (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended	12 Months Ended			6 Months Ended																				3 Months Ended																		3 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Second lien Curve	Jun. 30, 2013 Second lien	Dec. 31, 2011 Second lien	Mar. 31, 2013 Second lien	Dec. 31, 2012 Second lien	Jun. 30, 2013 Second lien Minimum	Jun. 30, 2013 Second lien Maximum	Jun. 30, 2013 Close ended second lien		Mar. 31, 2013 Close ended second lien		Dec. 31, 2012 Close ended second lien		Jun. 30, 2013 Close ended second lien Minimum		Mar. 31, 2013 Close ended second lien Minimum		Dec. 31, 2012 Close ended second lien Minimum		Jun. 30, 2013 Close ended second lien Maximum		Mar. 31, 2013 Close ended second lien Maximum		Dec. 31, 2012 Close ended second lien Maximum		Jun. 30, 2013 HELOCs		Mar. 31, 2013 HELOCs		Dec. 31, 2012 HELOCs		Jun. 30, 2013 HELOCs Minimum		Mar. 31, 2013 HELOCs Minimum		Dec. 31, 2012 HELOCs Minimum		Jun. 30, 2013 HELOCs Maximum		Mar. 31, 2013 HELOCs Maximum		Dec. 31, 2012 HELOCs Maximum		Jun. 30, 2013 Base Scenario Second lien	Dec. 31, 2011 Base Scenario Second lien	Jan. 31, 2012 Scenario 1 [Member] Second lien	Jun. 30, 2013 Scenario 1 [Member] Second lien	Dec. 31, 2011 Scenario 1 [Member] Second lien	Jun. 30, 2013 Scenario 1 [Member] Close ended second lien	Jun. 30, 2013 Scenario 1 [Member] HELOCs	Jan. 31, 2012 Scenario 2 [Member] Second lien	Jun. 30, 2013 Scenario 2 [Member] Second lien	Dec. 31, 2011 Scenario 2 [Member] Second lien	Jun. 30, 2013 Scenario 2 [Member] Close ended second lien	Jun. 30, 2013 Scenario 2 [Member] HELOCs
Guarantor Obligations [Line Items]
Period Company Reduced Base Scenario	2 months
Period Company Reduced Most Optimistic Case for Market Recovery	3 months
Plateau conditional default rate (as a percent)															7.30%	[1]	6.70%	[1]	7.30%	[1]	15.80%	[1]	18.60%	[1]	20.70%	[1]							3.40%	[1]	5.00%	[1]	3.80%	[1]	9.80%	[1]	17.20%	[1]	15.90%	[1]
Final conditional default rate trended down to (as a percent)															3.50%	[1]	3.50%	[1]	3.50%	[1]	9.10%	[1]	9.10%	[1]	9.10%	[1]							0.40%	[1]	0.40%	[1]	0.40%	[1]	3.20%	[1]	3.20%	[1]	3.20%	[1]
Conditional Default Rate Stress Period									34 months	[1]	36 months	[1]	36 months														34 months		36 months		36 months	[1]
Initial conditional prepayment rate (as a percent)															1.70%	[1]	2.70%	[1]	1.90%	[1]	14.00%	[1]	13.40%	[1]	12.50%	[1]							2.10%	[1]	2.40%	[1]	2.90%	[1]	20.10%	[1]	18.90%	[1]	15.40%	[1]
Final conditional prepayment rate (as a percent)		10.00%	10.00%						10.00%	[1]	10.00%	[1]	10.00%	[1]													10.00%	[1]	10.00%	[1]	10.00%	[1]
Loss severity (as a percent)									98.00%	[1]	98.00%	[1]	98.00%	[1]													98.00%	[1]	98.00%	[1]	98.00%	[1]
Initial draw rate (as a percent)																																	0.00%	[1]	0.00%	[1]	0.00%	[1]	3.30%	[1]	3.30%	[1]	4.80%	[1]
Typical past due period for loans to be charged off (in days)		180 days	180 days
First delinquency category (in days)							30 days	59 days
Second delinquency category (in days)							60 days	89 days
Third delinquency category (in days)							90 days	119 days
Fourth delinquency category (in days)							120 days	149 days
Fifth delinquency category (in days)							150 days	179 days
Period of Default Estimate			5 months
Number of Preceding Months Liquidation Rates Used to Estimate Loan Default Rate			12 months
Number of Months the Conditional Default Rate is Calculated Applying Liquidation Rates to Current Period Past Due Balances Excluding Thirty to Fifty Nine Days Past Due			4 months
Period of decrease in conditional default rate until final rate is achieved (in months)			28																																										28	30 months		33 months	30 months					24 months
Stress period (in months)			34																																										34	36 months		42 months	39 months				24	30 months
Number of Monthly Delinquency Categories			5 months
Period of constant conditional default rate (in months)			1 month																																										1 month	1 month							1 month
Loss Recovery Assumption		2.00%	2.00%		2.00%	2.00%
Conditional Prepayment Rate Base Case Average Number of Months			3 months
Period from Initial to Final Draw Rate																											3 months
Final Draw Rate																																	0.00%						1.60%
Number of conditional default rate curves modeled in estimating losses		3
Increased plateau period used to calculate potential change in loss estimate (in months)				1 month																																											4 months	4 months	4 months			1 month
Loss Estimate Sensitivity Analysis Increase in Conditional Default Rate Ramp Down Period	5 months
Loss Estimate Sensitivity Analysis Change in Estimate for Increased Conditional Default Rate Plateau Period																																																		$ 3	$ 47
Decreased ramp down period used to calculate potential change in loss estimate (in months)																																																					18
Loss Estimate Sensitivity Analysis Change in Estimate for Decreased Conditional Default Rate Ramp Down Period																																																							$ 2	$ 47

[1] Represents variables for most heavily weighted scenario (the “base case”).