- Quantitative Information - Assets (Details) - Income Approach Valuation Technique [Member] - Level 3 [Member] - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2016		Dec. 31, 2015
Obligations of state and political subdivisions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 7		$ 8
Corporate securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 74	[1],[2],[3]	$ 71	[4],[5],[6]
Yield (as a percent)		20.20%	[1],[2],[3]	21.80%	[4],[5],[6]
RMBS [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 360	[1],[2],[3]	$ 348	[4],[5],[6]
RMBS [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		3.90%	[1],[2],[3]	4.70%	[4],[5],[6]
Conditional prepayment rate (as a percent)		1.00%	[1],[2],[3]	0.30%	[4],[5],[6]
Conditional default rate (as a percent)		4.80%	[1],[2],[3]	2.70%	[4],[5],[6]
Loss severity rate (as a percent)		65.00%	[1],[2],[3]	60.00%	[4],[5],[6]
RMBS [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		8.90%	[1],[2],[3]	8.20%	[4],[5],[6]
Conditional prepayment rate (as a percent)		9.80%	[1],[2],[3]	9.00%	[4],[5],[6]
Conditional default rate (as a percent)		12.80%	[1],[2],[3]	9.30%	[4],[5],[6]
Loss severity rate (as a percent)		100.00%	[1],[2],[3]	100.00%	[4],[5],[6]
RMBS [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		6.00%	[1],[2],[3]	6.00%	[4],[5],[6]
Conditional prepayment rate (as a percent)		2.80%	[1],[2],[3]	2.60%	[4],[5],[6]
Conditional default rate (as a percent)		9.70%	[1],[2],[3]	7.00%	[4],[5],[6]
Loss severity rate (as a percent)		78.00%	[1],[2],[3]	74.00%	[4],[5],[6]
Investor-owned utilities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 71	[1],[3]	$ 69	[4],[6]
Cash flow receipts (as a percent)		100.00%	[1],[3]	100.00%	[4],[6]
Discount factor (as a percent)		7.00%	[1],[3]	7.00%	[4],[6]
Collateral recovery period (in years)		2 years 8 months	[1],[3]	2 years 11 months	[4],[6]
Triple-X Life Insurance Transaction [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 321	[1],[3]	$ 329	[4],[6]
Triple-X Life Insurance Transaction [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		3.50%	[1],[3]	3.50%	[4],[6]
Triple-X Life Insurance Transaction [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		7.30%	[1],[3]	7.50%	[4],[6]
Triple-X Life Insurance Transaction [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		4.90%	[1],[3]	5.00%	[4],[6]
Pooled corporate obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 247	[1],[3]	$ 259	[4],[6]
Discount factor (as a percent)		15.00%	[1],[3]	20.00%	[4],[6]
Short-term Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value	[4],[6]			$ 60
Yield (as a percent)	[4],[6]			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		$ 1,191	[1],[3]	$ 1,261	[4],[6]
Financial Guaranty Variable Interest Entities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		3.50%	[1],[3]	1.90%	[4],[6]
Conditional prepayment rate (as a percent)		2.50%	[1],[3]	0.30%	[4],[6]
Conditional default rate (as a percent)		1.20%	[1],[3]	1.20%	[4],[6]
Loss severity rate (as a percent)		40.00%	[1],[3]	40.00%	[4],[6]
Financial Guaranty Variable Interest Entities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		20.90%	[1],[3]	20.00%	[4],[6]
Conditional prepayment rate (as a percent)		8.60%	[1],[3]	9.20%	[4],[6]
Conditional default rate (as a percent)		23.10%	[1],[3]	16.00%	[4],[6]
Loss severity rate (as a percent)		100.00%	[1],[3]	100.00%	[4],[6]
Financial Guaranty Variable Interest Entities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield (as a percent)		6.80%	[1],[3]	6.40%	[4],[6]
Conditional prepayment rate (as a percent)		5.10%	[1],[3]	3.90%	[4],[6]
Conditional default rate (as a percent)		5.60%	[1],[3]	4.70%	[4],[6]
Loss severity rate (as a percent)		86.80%	[1],[3]	85.90%	[4],[6]
Other Assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Asset, fair value		$ 46	[1],[3]	$ 62	[4],[6]
Fair Value Inputs Term		5 years	[1],[3]	5 years	[4],[6]
Other Assets [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		$ 51	[1],[3]	$ 44	[4],[6]
Other Assets [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		54	[1],[3]	46	[4],[6]
Other Assets [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Quotes from third party pricing (in dollars per share)		$ 53	[1],[3]	$ 45	[4],[6]

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

[2] Excludes obligations of state and political subdivisions investments with fair value of $7 million.

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

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

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

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