Fair Value Measurement -Quantitative Information - Liabilities (Details) (Income Approach Valuation Technique, Level 3, USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Credit derivative liabilities, net
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Total liabilities carried at fair value	$ (1,568)	[1]	$ (1,693)	[1]
Credit derivative liabilities, net | Minimum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Internal floor (as a percent)	700.00%		700.00%
Bank profit (as a percent)	100.00%		100.00%
Hedge cost (as a percent)	3000.00%		4630.00%
Year 1 loss estimates (as a percent)	0.00%		0.00%
Credit derivative liabilities, net | Maximum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Internal floor (as a percent)	10000.00%		10000.00%
Bank profit (as a percent)	145090.00%		141850.00%
Hedge cost (as a percent)	34500.00%		52500.00%
Year 1 loss estimates (as a percent)	63.00%		48.00%
Credit derivative liabilities, net | Weighted Average
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Internal floor (as a percent)	1390.00%		1560.00%
Bank profit (as a percent)	11350.00%		25040.00%
Hedge cost (as a percent)	7330.00%		11010.00%
Year 1 loss estimates (as a percent)	2.10%		1.90%
Financial guaranty, variable interest entities
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Total liabilities carried at fair value	$ (1,459)	[1]	$ (2,871)	[1]
Financial guaranty, variable interest entities | Minimum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Loss severity rate (as a percent)	45.00%		37.50%
Conditional default rate (as a percent)	1.20%		3.00%
Conditional prepayment rate (as a percent)	0.00%		0.30%
Yield (as a percent)	2.50%		3.50%
Financial guaranty, variable interest entities | Maximum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Loss severity rate (as a percent)	100.00%		102.00%
Conditional default rate (as a percent)	13.30%		25.80%
Conditional prepayment rate (as a percent)	11.40%		11.80%
Yield (as a percent)	7.70%		10.20%
Financial guaranty, variable interest entities | Weighted Average
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Loss severity rate (as a percent)	85.40%		94.60%
Conditional default rate (as a percent)	6.50%		13.60%
Conditional prepayment rate (as a percent)	3.60%		3.60%
Yield (as a percent)	5.20%		5.40%

[1] (1)Discounted cash flow is used as valuation technique for all financial instruments.