- 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, 2016		Dec. 31, 2015
Obligations of state and political subdivisions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 41	[1],[2]	$ 8
Obligations of state and political subdivisions [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	[1],[2]	4.30%
Obligations of state and political subdivisions [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	[1],[2]	18.40%
Obligations of state and political subdivisions [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)	[1],[2]	13.20%
Corporate securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 58	[1],[2]	$ 71	[3],[4],[5]
Yield (as a percent)		20.30%	[1],[2]	21.80%	[3],[4],[5]
RMBS [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 349	[1],[2]	$ 348	[3],[4],[5]
RMBS [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		4.80%	[1],[2]	4.70%	[3],[4],[5]
Conditional prepayment rate (as a percent)		1.60%	[1],[2]	0.30%	[3],[4],[5]
Conditional default rate (as a percent)		0.10%	[1],[2]	2.70%	[3],[4],[5]
Loss severity rate (as a percent)		50.00%	[1],[2]	60.00%	[3],[4],[5]
RMBS [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		8.50%	[1],[2]	8.20%	[3],[4],[5]
Conditional prepayment rate (as a percent)		9.50%	[1],[2]	9.00%	[3],[4],[5]
Conditional default rate (as a percent)		12.40%	[1],[2]	9.30%	[3],[4],[5]
Loss severity rate (as a percent)		100.00%	[1],[2]	100.00%	[3],[4],[5]
RMBS [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		6.00%	[1],[2]	6.00%	[3],[4],[5]
Conditional prepayment rate (as a percent)		3.30%	[1],[2]	2.60%	[3],[4],[5]
Conditional default rate (as a percent)		9.40%	[1],[2]	7.00%	[3],[4],[5]
Loss severity rate (as a percent)		75.20%	[1],[2]	74.00%	[3],[4],[5]
Investor-owned utilities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[3],[5]			$ 69
Cash flow receipts (as a percent)	[3],[5]			100.00%
Discount factor (as a percent)	[3],[5]			7.00%
Collateral recovery period (in years)	[3],[5]			2 years 11 months
Triple-X Life Insurance Transaction [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 321	[1],[2]	$ 329	[3],[5]
Triple-X Life Insurance Transaction [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		4.30%	[1],[2]	3.50%	[3],[5]
Triple-X Life Insurance Transaction [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		6.80%	[1],[2]	7.50%	[3],[5]
Triple-X Life Insurance Transaction [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		5.10%	[1],[2]	5.00%	[3],[5]
Pooled corporate obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 243	[1],[2]	$ 259	[3],[5]
Discount factor (as a percent)		15.00%	[1],[2]	20.00%	[3],[5]
Short-term Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[3],[5]			$ 60
Yield (as a percent)	[3],[5]			17.00%
Other invested assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 7		$ 7
Financial Guaranty Variable Interest Entities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 814	[1],[2]	$ 1,261	[3],[5]
Financial Guaranty Variable Interest Entities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		3.20%	[1],[2]	1.90%	[3],[5]
Conditional prepayment rate (as a percent)		2.50%	[1],[2]	0.30%	[3],[5]
Conditional default rate (as a percent)		1.20%	[1],[2]	1.20%	[3],[5]
Loss severity rate (as a percent)		50.00%	[1],[2]	40.00%	[3],[5]
Financial Guaranty Variable Interest Entities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		21.50%	[1],[2]	20.00%	[3],[5]
Conditional prepayment rate (as a percent)		8.00%	[1],[2]	9.20%	[3],[5]
Conditional default rate (as a percent)		16.30%	[1],[2]	16.00%	[3],[5]
Loss severity rate (as a percent)		100.00%	[1],[2]	100.00%	[3],[5]
Financial Guaranty Variable Interest Entities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		7.00%	[1],[2]	6.40%	[3],[5]
Conditional prepayment rate (as a percent)		5.10%	[1],[2]	3.90%	[3],[5]
Conditional default rate (as a percent)		5.80%	[1],[2]	4.70%	[3],[5]
Loss severity rate (as a percent)		85.40%	[1],[2]	85.90%	[3],[5]
Other Assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 35	[1],[2]	$ 62	[3],[5]
Fair Value Inputs Term		5 years	[1],[2]	5 years	[3],[5]
Other Assets [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		$ 59	[1],[2]	$ 44	[3],[5]
Other Assets [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		61	[1],[2]	46	[3],[5]
Other Assets [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		$ 60	[1],[2]	$ 45	[3],[5]

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

[2] Excludes several investments recorded in other invested assets with fair value of $7 million.

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

[4] Excludes obligations of state and political subdivisions investments with fair value of $8 million.

[5] Excludes several investments recorded in other invested assets with fair value of $7 million.