Fair Value Measurements - Financial Assets and Financial Liabilities Carried at Fair Value (Details) $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2015 USD ($)		Dec. 31, 2014 USD ($)
Financial assets at fair value:
Fixed maturities		$ 18,569		$ 18,983
Equity securities		189		189
Short-term investments		97		163
Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		18,569	[1]	18,983	[2]
Equity securities		189		189
Subtotal		18,758		19,172
Short-term investments		97		163
Total financial assets at fair value, excluding separate accounts		19,734		20,294
Financial liabilities at fair value:
Total financial liabilities at fair value		841		930
Run-off Settlement Annuity Business [Member] | Fair Value, Measurements, Recurring [Member]
Financial liabilities at fair value:
Net appreciation required to adjust future policy benefits for run-off settlement annuity business included in fixed maturities		558		756
Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		12	[3]	6	[4]
Financial liabilities at fair value:
Derivative liabilities	[4]			1
Other derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		12		5
Financial liabilities at fair value:
Derivative liabilities				1
Other derivatives [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		0		1
Other derivatives [Member] | Non designated [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		$ 0		0
Financial liabilities at fair value:
Derivative liabilities				$ 0
Guaranteed Minimum Income Benefit [Member]
Financial liabilities at fair value:
Number of external reinsurers		3		3
Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		$ 867	[5]	$ 953	[6]
Financial liabilities at fair value:
Derivative liabilities		841		929
Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		829		954
State and local government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		1,771		1,856
Foreign government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		1,957		1,940
Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		13,436		13,498
Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		57		85
Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		519		650
Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		249	[1]	290	[2]
Equity securities		33		61
Subtotal		282		351
Short-term investments		0		0
Total financial assets at fair value, excluding separate accounts		282		351
Financial liabilities at fair value:
Total financial liabilities at fair value		0		0
Fair Value Inputs Level 1 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		0	[3]	0	[4]
Financial liabilities at fair value:
Derivative liabilities	[4]			0
Fair Value Inputs Level 1 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		0	[5]	0	[6]
Financial liabilities at fair value:
Derivative liabilities		0		0
Fair Value Inputs Level 1 [Member] | Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		249		290
Fair Value Inputs Level 1 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 1 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 1 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 1 [Member] | Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 1 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		17,708	[1]	17,879	[2]
Equity securities		102		85
Subtotal		17,810		17,964
Short-term investments		97		163
Total financial assets at fair value, excluding separate accounts		17,919		18,133
Financial liabilities at fair value:
Total financial liabilities at fair value		0		1
Fair Value Inputs Level 2 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		12	[3]	6	[4]
Financial liabilities at fair value:
Derivative liabilities	[4]			1
Fair Value Inputs Level 2 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		0	[5]	0	[6]
Financial liabilities at fair value:
Derivative liabilities		0		0
Fair Value Inputs Level 2 [Member] | Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		580		664
Fair Value Inputs Level 2 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		1,771		1,856
Fair Value Inputs Level 2 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		1,953		1,936
Fair Value Inputs Level 2 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		13,144		13,105
Fair Value Inputs Level 2 [Member] | Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		56		84
Fair Value Inputs Level 2 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		204		234
Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		612	[1]	814	[2]
Equity securities		54		43
Subtotal		666		857
Short-term investments		0		0
Total financial assets at fair value, excluding separate accounts		1,533		1,810
Financial liabilities at fair value:
Total financial liabilities at fair value		841		929
Fair Value Inputs Level 3 [Member] | Run-off Settlement Annuity Business [Member] | Fair Value, Measurements, Recurring [Member]
Financial liabilities at fair value:
Net appreciation required to adjust future policy benefits for run-off settlement annuity business included in fixed maturities		32		65
Fair Value Inputs Level 3 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		0	[3]	0	[4]
Financial liabilities at fair value:
Derivative liabilities	[4]			0
Fair Value Inputs Level 3 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets		867	[5]	953	[6]
Financial liabilities at fair value:
Derivative liabilities		841		929
Fair Value Inputs Level 3 [Member] | Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 3 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		0		0
Fair Value Inputs Level 3 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		4		4
Fair Value Inputs Level 3 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		292		393
Fair Value Inputs Level 3 [Member] | Mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		1		1
Fair Value Inputs Level 3 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities		$ 315		$ 416

[1] Fixed maturities included $558 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $32 million of appreciation for securities classified in Level 3. See Note 8 for additional information.

[2] Fixed maturities included $756 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $65 million of appreciation for securities classified in Level 3. See Note 8 for additional information.

[3] Other derivative assets included $12 million of interest rate and foreign currency swaps qualifying as cash flow hedges. See Note 9 for additional information.

[4] Other derivative assets included $5 million of interest rate and foreign currency swaps qualifying as cash flow hedges and $1 million of interest rate swaps qualifying as fair value hedges. Other derivative liabilities reflected interest rate and foreign currency swaps qualifying as cash flow hedges. See Note 9 for additional information.

[5] The GMIB assets represent retrocessional contracts in place from three external reinsurers that cover the exposures on these contracts.

[6] The GMIB assets represented retrocessional contracts in place from three external reinsurers that cover the exposures on these contracts.