Fair Value Measurements - Financial Assets and Financial Liabilities Carried at Fair Value (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Financial assets at fair value:
Fixed maturities	$ 17,650		$ 16,486
Equity securities	127		141
Short-term investments	394		631
Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	17,650	[1]	16,486	[2]
Equity securities	127		141
Subtotal	17,777		16,627
Short-term investments	394		631
Total financial assets at fair value, excluding separate accounts	18,988		18,012
Financial liabilities at fair value:
Total financial liabilities at fair value	810		757
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	605		458
Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets	2	[3]	3	[4]
Financial liabilities at fair value:
Derivative liabilities	16	[3]	16	[4]
Other derivatives [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets	2		3
Financial liabilities at fair value:
Derivative liabilities	16		15
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		1
Guaranteed Minimum Income Benefit [Member]
Financial liabilities at fair value:
Percentage of GMIB exposure covered by retrocessional coverage	100.00%		100.00%
Number of external reinsurers	3		3
Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets	815	[5]	751	[6]
Financial liabilities at fair value:
Derivative liabilities	794		741
Federal government and agency [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	1,128		880
State and local government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	2,096		2,144
Foreign government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	1,583		1,444
Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	11,814		10,981
Federal agency mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	71		76
Other mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	80		77
Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	878		884
Fair Value Inputs Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	497	[1]	297	[2]
Equity securities	1		8
Subtotal	498		305
Short-term investments	0		0
Total financial assets at fair value, excluding separate accounts	498		305
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	0	[3]	0	[4]
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	497		297
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] | Federal agency mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	0		0
Fair Value Inputs Level 1 [Member] | Other 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	16,003	[1]	15,058	[2]
Equity securities	78		74
Subtotal	16,081		15,132
Short-term investments	394		631
Total financial assets at fair value, excluding separate accounts	16,477		15,766
Financial liabilities at fair value:
Total financial liabilities at fair value	16		16
Fair Value Inputs Level 2 [Member] | Other derivatives [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets	2	[3]	3	[4]
Financial liabilities at fair value:
Derivative liabilities	16	[3]	16	[4]
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	631		583
Fair Value Inputs Level 2 [Member] | State and local government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	2,096		2,144
Fair Value Inputs Level 2 [Member] | Foreign government [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	1,557		1,421
Fair Value Inputs Level 2 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	11,309		10,476
Fair Value Inputs Level 2 [Member] | Federal agency mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	71		76
Fair Value Inputs Level 2 [Member] | Other mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	79		76
Fair Value Inputs Level 2 [Member] | Other asset-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	260		282
Fair Value Inputs Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	1,150	[1]	1,131	[2]
Equity securities	48		59
Subtotal	1,198		1,190
Short-term investments	0		0
Total financial assets at fair value, excluding separate accounts	2,013		1,941
Financial liabilities at fair value:
Total financial liabilities at fair value	794		741
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	82		60
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	0	[3]	0	[4]
Fair Value Inputs Level 3 [Member] | Guaranteed Minimum Income Benefit [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Derivative assets	815	[5]	751	[6]
Financial liabilities at fair value:
Derivative liabilities	794		741
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	26		23
Fair Value Inputs Level 3 [Member] | Corporate [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	505		505
Fair Value Inputs Level 3 [Member] | Federal agency mortgage-backed [Member] | Fair Value, Measurements, Recurring [Member]
Financial assets at fair value:
Fixed maturities	0		0
Fair Value Inputs Level 3 [Member] | Other 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	$ 618		$ 602

[1] Fixed maturities included $605 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $82 million of appreciation for securities classified in Level 3.

[2] Fixed maturities included $458 million of net appreciation required to adjust future policy benefits for the run-off settlement annuity business including $60 million of appreciation for securities classified in Level 3.

[3] Other derivative assets and other derivative liabilities reflected foreign currency and interest rate swaps qualifying as cash flow hedges. See Note 9 for additional information.

[4] Other derivative assets reflected interest rate and foreign currency swaps qualifying as cash flow hedges. Other derivative liabilities included $15 million of interest rate and foreign currency swaps qualifying as cash flow hedges and $1 million of interest rate and foreign currency swaps not designated as accounting 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. See Note 5 for additional information.

[6] The GMIB assets represented retrocessional contracts in place from three external reinsurers that cover the exposures on these contracts. See Note 5 for additional information.