Investments and Derivative Instruments Level 4 Credit Derivatives (Details) - Hedging Designation [Domain] - Hedging Relationship [Domain] - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Mar. 31, 2013
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 49,064,000,000	$ 55,838,000,000	$ 55,838,000,000
Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	2,151,000,000	2,034,000,000
Credit Risk Derivatives, at Fair Value, Net	147,000,000	148,000,000
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	177,000,000	212,000,000
Credit Risk Derivatives, at Fair Value, Net	$ 2,000,000	$ 3,000,000
Average Term of Credit Risk Derivatives	2 years	3 years
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BB Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 4,000,000	$ 4,000,000
Credit Risk Derivatives, at Fair Value, Net	$ 0	$ 0
Average Term of Credit Risk Derivatives	3 months	1 year
Basket Credit Default Swaps [Member]
Credit Derivatives Footnote [Abstract]
Amount of Standard Market Indices of Diversified Portfolios of Corporate Issuers	$ 1,800,000,000	$ 1,700,000,000
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	1,157,000,000	1,240,000,000
Credit Risk Derivatives, at Fair Value, Net	$ 16,000,000	$ 14,000,000
Average Term of Credit Risk Derivatives	4 years	4 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, B Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 31,000,000	$ 9,000,000
Credit Risk Derivatives, at Fair Value, Net	$ 2,000,000	$ (1,000,000)
Average Term of Credit Risk Derivatives	5 years	5 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AA+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 557,000,000	$ 344,000,000
Credit Risk Derivatives, at Fair Value, Net	$ (11,000,000)	$ (4,000,000)
Average Term of Credit Risk Derivatives	6 years	5 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, CCC+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 75,000,000	$ 75,000,000
Credit Risk Derivatives, at Fair Value, Net	$ (11,000,000)	$ (11,000,000)
Average Term of Credit Risk Derivatives	2 years	2 years
Embedded Derivative Financial Instruments [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 150,000,000	$ 150,000,000
Credit Risk Derivatives, at Fair Value, Net	$ 149,000,000	$ 147,000,000
Average Term of Credit Risk Derivatives	2 years	2 years
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 753,000,000	$ 1,088,000,000
Credit Risk Derivatives, at Fair Value, Net	5,000,000	4,000,000
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	152,000,000	163,000,000
Credit Risk Derivatives, at Fair Value, Net	(3,000,000)	(3,000,000)
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BB Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	4,000,000	4,000,000
Credit Risk Derivatives, at Fair Value, Net	0	0
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	346,000,000	667,000,000
Credit Risk Derivatives, at Fair Value, Net	(4,000,000)	(6,000,000)
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, B Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	0	0
Credit Risk Derivatives, at Fair Value, Net	0	0
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AA+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	176,000,000	179,000,000
Credit Risk Derivatives, at Fair Value, Net	1,000,000	2,000,000
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, CCC+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	75,000,000	75,000,000
Credit Risk Derivatives, at Fair Value, Net	11,000,000	11,000,000
Credit Derivatives in Offsetting Positions [Member] | Embedded Derivative Financial Instruments [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	0	0
Credit Risk Derivatives, at Fair Value, Net	$ 0	$ 0