- Quantitative Information - Assets (Details) - Income Approach Valuation Technique [Member] - Level 3 [Member] - USD ($) $ / shares in Units, $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Obligations of state and political subdivisions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 7	$ 38
Yield (as a percent)		4.60%
Obligations of state and political subdivisions [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Rate of inflation (as a percent)		1.00%	1.00%
Cash flow receipts (as a percent)		0.50%	0.50%
Yield (as a percent)			4.60%
Collateral recovery period (in years)		1 month	1 month
Obligations of state and political subdivisions [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Rate of inflation (as a percent)		3.00%	3.00%
Cash flow receipts (as a percent)		21.20%	74.30%
Yield (as a percent)			8.00%
Collateral recovery period (in years)		8 years 1 month	34 years
Obligations of state and political subdivisions [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Rate of inflation (as a percent)		2.00%	2.00%
Cash flow receipts (as a percent)		13.10%	63.00%
Yield (as a percent)			7.30%
Collateral recovery period (in years)		4 years	28 years
Corporate securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 77	$ 79
Yield (as a percent)		18.70%	17.80%
RMBS [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 335	$ 425
RMBS [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		4.60%	4.70%
Conditional prepayment rate (as a percent)		0.30%	0.30%
Conditional default rate (as a percent)		2.20%	2.70%
Loss severity rate (as a percent)		57.00%	52.60%
RMBS [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		9.50%	11.70%
Conditional prepayment rate (as a percent)		7.50%	8.10%
Conditional default rate (as a percent)		12.10%	10.60%
Loss severity rate (as a percent)		100.00%	100.00%
RMBS [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		6.00%	6.40%
Conditional prepayment rate (as a percent)		2.90%	3.30%
Conditional default rate (as a percent)		5.20%	5.30%
Loss severity rate (as a percent)		75.40%	75.20%
Investor-owned utilities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 98	$ 95
Cash flow receipts (as a percent)		100.00%	100.00%
Discount factor (as a percent)		7.00%	7.00%
Collateral recovery period (in years)		3 years 5 months	4 years
XXX life insurance transactions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 138	$ 133
Yield (as a percent)		7.30%	7.30%
Other invested assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 83	$ 83
Liquidity discount (as a percent)		20.00%	20.00%
Recovery on delinquent loans (as a percent)		40.00%	40.00%
Other invested assets [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Conditional prepayment rate (as a percent)		8.00%	5.00%
Conditional default rate (as a percent)		0.00%	0.00%
Loss severity rate (as a percent)		40.00%	40.00%
Net asset value (per share)		$ 978	$ 965
Other invested assets [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Conditional prepayment rate (as a percent)		15.00%	15.00%
Conditional default rate (as a percent)		5.00%	7.00%
Loss severity rate (as a percent)		75.00%	75.00%
Net asset value (per share)		$ 1,162	$ 1,159
Other invested assets [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Conditional prepayment rate (as a percent)		12.30%	12.30%
Conditional default rate (as a percent)		4.50%	5.80%
Loss severity rate (as a percent)		68.50%	68.30%
Net asset value (per share)		$ 1,060	$ 1,082
Financial Guaranty Variable Interest Entities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 1,596	$ 1,398
Financial Guaranty Variable Interest Entities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		1.50%	2.70%
Conditional prepayment rate (as a percent)		0.30%	0.30%
Conditional default rate (as a percent)		1.60%	1.60%
Loss severity rate (as a percent)		40.00%	40.00%
Financial Guaranty Variable Interest Entities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		16.60%	17.70%
Conditional prepayment rate (as a percent)		11.50%	11.00%
Conditional default rate (as a percent)		18.50%	11.80%
Loss severity rate (as a percent)		100.00%	100.00%
Financial Guaranty Variable Interest Entities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		6.10%	7.90%
Conditional prepayment rate (as a percent)		3.50%	3.30%
Conditional default rate (as a percent)		5.40%	5.10%
Loss severity rate (as a percent)		80.80%	82.20%
Other Assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[1]	$ 60	$ 35
Fair Value Inputs Term		5 years	5 years
Other Assets [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		$ 41	$ 52
Other Assets [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		46	61
Other Assets [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		$ 44	$ 57

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