Fair Value Measurements - Assets and Liabilities by Level (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Fixed maturities:
Total fixed maturities	$ 15,767		$ 17,705
Equity securities	122		111
Short-term investments	296		154
Financial liabilities at fair value:
Percentage of GMIB exposure covered by retrocessional coverage			55.00%
Variable Annuity [Member] | Guaranteed Minimum Income Benefit [Member]
Financial liabilities at fair value:
Ceded Credit Risk, Number Of External Reinsurers	3		2
Fair Value, Measurements, Recurring [Member]
Fixed maturities:
Federal government and agency	750		902
State and local government	2,276		2,437
Foreign government	1,195		1,322
Corporate	10,520		11,896
Federal agency mortgage-backed	92		122
Other mortgage-backed	64		89
Other asset-backed	870		937
Total fixed maturities	15,767	[1]	17,705	[2]
Equity securities	122		111
Subtotal	15,889		17,816
Short-term investments	296		154
GMIB assets	945	[3]	622	[4]
Other derivative assets	5	[5]	41	[6]
Total financial assets at fair value, excluding separate accounts	17,135		18,633
Financial liabilities at fair value:
GMIB liabilities	922		1,170
Other derivative liabilities	17	[5]	31	[6]
Total financial liabilities at fair value	939		1,201
Unrealized Appreciation Settlement Annuity	602		875
Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fixed maturities:
Federal government and agency	97		156
State and local government	0		0
Foreign government	0		0
Corporate	0		0
Federal agency mortgage-backed	0		0
Other mortgage-backed	0		0
Other asset-backed	0		0
Total fixed maturities	97	[1]	156	[2]
Equity securities	6		4
Subtotal	103		160
Short-term investments	0		0
GMIB assets	0	[3]	0	[4]
Other derivative assets	0	[5]	0	[6]
Total financial assets at fair value, excluding separate accounts	103		160
Financial liabilities at fair value:
GMIB liabilities	0		0
Other derivative liabilities	0	[5]	0	[6]
Total financial liabilities at fair value	0		0
Fair Value Inputs Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fixed maturities:
Federal government and agency	653		746
State and local government	2,276		2,437
Foreign government	1,173		1,298
Corporate	9,983		11,201
Federal agency mortgage-backed	92		122
Other mortgage-backed	63		88
Other asset-backed	256		340
Total fixed maturities	14,496	[1]	16,232	[2]
Equity securities	81		73
Subtotal	14,577		16,305
Short-term investments	296		154
GMIB assets	0	[3]	0	[4]
Other derivative assets	5	[5]	41	[6]
Total financial assets at fair value, excluding separate accounts	14,878		16,500
Financial liabilities at fair value:
GMIB liabilities	0		0
Other derivative liabilities	17	[5]	31	[6]
Total financial liabilities at fair value	17		31
Fair Value Inputs Level 2 [Member] | Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member]
Fixed maturities:
Other derivative assets	5		5
Fair Value Inputs Level 2 [Member] | Non designated [Member] | Fair Value, Measurements, Recurring [Member]
Fixed maturities:
Other derivative assets			36
Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fixed maturities:
Federal government and agency	0		0
State and local government	0		0
Foreign government	22		24
Corporate	537		695
Federal agency mortgage-backed	0		0
Other mortgage-backed	1		1
Other asset-backed	614		597
Total fixed maturities	1,174	[1]	1,317	[2]
Equity securities	35		34
Subtotal	1,209		1,351
Short-term investments	0		0
GMIB assets	945	[3]	622	[4]
Other derivative assets	0	[5]	0	[6]
Total financial assets at fair value, excluding separate accounts	2,154		1,973
Financial liabilities at fair value:
GMIB liabilities	922		1,170
Other derivative liabilities	0	[5]	0	[6]
Total financial liabilities at fair value	922		1,170
Unrealized Appreciation Settlement Annuity	$ 69		$ 108

[1] Fixed maturities included $602 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $69 million of appreciation for securities classified in Level 3.

[2] Fixed maturities included $875 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $108 million of appreciation for securities classified in Level 3.

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

[4] The GMIB assets represent retrocessional contracts in place from two external reinsurers that covered 55% of the exposures on these contracts.

[5] Other derivative assets included $5 million of interest rate and foreign currency swaps qualifying as cash flow hedges. Other derivative liabilities reflected foreign currency and interest rate swaps qualifying as cash flow hedges. See Note 10 for additional information.

[6] Other derivative assets included $5 million of interest rate and foreign currency swaps qualifying as cash flow hedges and $36 million of interest rate swaps not designated as accounting hedges. Other derivative liabilities reflected foreign currency and interest rate swaps qualifying as cash flow hedges. See Note 10 for additional information.